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Dates

TheDates module provides two types for working with dates:Date andDateTime, representing day and millisecond precision, respectively; both are subtypes of the abstractTimeType. The motivation for distinct types is simple: some operations are much simpler, both in terms of code and mental reasoning, when the complexities of greater precision don't have to be dealt with. For example, since theDate type only resolves to the precision of a single date (i.e. no hours, minutes, or seconds), normal considerations for time zones, daylight savings/summer time, and leap seconds are unnecessary and avoided.

BothDate andDateTime are basically immutableInt64 wrappers. The singleinstant field of either type is actually aUTInstant{P} type, which represents a continuously increasing machine timeline based on the UT second[1]. TheDateTime type is not aware of time zones (naive, in Python parlance), analogous to aLocalDateTime in Java 8. Additional time zone functionality can be added through theTimeZones.jl package, which compiles theIANA time zone database. BothDate andDateTime are based on theISO 8601 standard, which follows the proleptic Gregorian calendar. One note is that the ISO 8601 standard is particular about BC/BCE dates. In general, the last day of the BC/BCE era, 1-12-31 BC/BCE, was followed by 1-1-1 AD/CE, thus no year zero exists. The ISO standard, however, states that 1 BC/BCE is year zero, so0000-12-31 is the day before0001-01-01, and year-0001 (yes, negative one for the year) is 2 BC/BCE, year-0002 is 3 BC/BCE, etc.

Constructors

Date andDateTime types can be constructed by integer orPeriod types, by parsing, or through adjusters (more on those later):

julia> DateTime(2013)2013-01-01T00:00:00julia> DateTime(2013,7)2013-07-01T00:00:00julia> DateTime(2013,7,1)2013-07-01T00:00:00julia> DateTime(2013,7,1,12)2013-07-01T12:00:00julia> DateTime(2013,7,1,12,30)2013-07-01T12:30:00julia> DateTime(2013,7,1,12,30,59)2013-07-01T12:30:59julia> DateTime(2013,7,1,12,30,59,1)2013-07-01T12:30:59.001julia> Date(2013)2013-01-01julia> Date(2013,7)2013-07-01julia> Date(2013,7,1)2013-07-01julia> Date(Dates.Year(2013),Dates.Month(7),Dates.Day(1))2013-07-01julia> Date(Dates.Month(7),Dates.Year(2013))2013-07-01

Date orDateTime parsing is accomplished by the use of format strings. Format strings work by the notion of definingdelimited orfixed-width "slots" that contain a period to parse and passing the text to parse and format string to aDate orDateTime constructor, of the formDate("2015-01-01",dateformat"y-m-d") orDateTime("20150101",dateformat"yyyymmdd").

Delimited slots are marked by specifying the delimiter the parser should expect between two subsequent periods; so"y-m-d" lets the parser know that between the first and second slots in a date string like"2014-07-16", it should find the- character. They,m, andd characters let the parser know which periods to parse in each slot.

As in the case of constructors above such asDate(2013), delimitedDateFormats allow for missing parts of dates and times so long as the preceding parts are given. The other parts are given the usual default values. For example,Date("1981-03", dateformat"y-m-d") returns1981-03-01, whilstDate("31/12", dateformat"d/m/y") gives0001-12-31. (Note that the default year is 1 AD/CE.) An empty string, however, always throws anArgumentError.

Fixed-width slots are specified by repeating the period character the number of times corresponding to the width with no delimiter between characters. Sodateformat"yyyymmdd" would correspond to a date string like"20140716". The parser distinguishes a fixed-width slot by the absence of a delimiter, noting the transition"yyyymm" from one period character to the next.

Support for text-form month parsing is also supported through theu andU characters, for abbreviated and full-length month names, respectively. By default, only English month names are supported, sou corresponds to "Jan", "Feb", "Mar", etc. AndU corresponds to "January", "February", "March", etc. Similar to other name=>value mapping functionsdayname andmonthname, custom locales can be loaded by passing in thelocale=>Dict{String,Int} mapping to theMONTHTOVALUEABBR andMONTHTOVALUE dicts for abbreviated and full-name month names, respectively.

The above examples used thedateformat"" string macro. This macro creates aDateFormat object once when the macro is expanded and uses the sameDateFormat object even if a code snippet is run multiple times.

julia> for i = 1:10^5           Date("2015-01-01", dateformat"y-m-d")       end

Or you can create the DateFormat object explicitly:

julia> df = DateFormat("y-m-d");julia> dt = Date("2015-01-01",df)2015-01-01julia> dt2 = Date("2015-01-02",df)2015-01-02

Alternatively, use broadcasting:

julia> years = ["2015", "2016"];julia> Date.(years, DateFormat("yyyy"))2-element Vector{Date}: 2015-01-01 2016-01-01

For convenience, you may pass the format string directly (e.g.,Date("2015-01-01","y-m-d")), although this form incurs performance costs if you are parsing the same format repeatedly, as it internally creates a newDateFormat object each time.

As well as via the constructors, aDate orDateTime can be constructed from strings using theparse andtryparse functions, but with an optional third argument of typeDateFormat specifying the format; for example,parse(Date, "06.23.2013", dateformat"m.d.y"), ortryparse(DateTime, "1999-12-31T23:59:59") which uses the default format. The notable difference between the functions is that withtryparse, an error is not thrown if the string is empty or in an invalid format; insteadnothing is returned.

Julia 1.9

Before Julia 1.9, empty strings could be passed to constructors andparse without error, returning as appropriateDateTime(1),Date(1) orTime(0). Likewise,tryparse did not returnnothing.

A full suite of parsing and formatting tests and examples is available instdlib/Dates/test/io.jl.

Durations/Comparisons

Finding the length of time between twoDate orDateTime is straightforward given their underlying representation asUTInstant{Day} andUTInstant{Millisecond}, respectively. The difference betweenDate is returned in the number ofDay, andDateTime in the number ofMillisecond. Similarly, comparingTimeType is a simple matter of comparing the underlying machine instants (which in turn compares the internalInt64 values).

julia> dt = Date(2012,2,29)2012-02-29julia> dt2 = Date(2000,2,1)2000-02-01julia> dump(dt)Date  instant: Dates.UTInstant{Day}    periods: Day      value: Int64 734562julia> dump(dt2)Date  instant: Dates.UTInstant{Day}    periods: Day      value: Int64 730151julia> dt > dt2truejulia> dt != dt2truejulia> dt + dt2ERROR: MethodError: no method matching +(::Date, ::Date)[...]julia> dt * dt2ERROR: MethodError: no method matching *(::Date, ::Date)[...]julia> dt / dt2ERROR: MethodError: no method matching /(::Date, ::Date)julia> dt - dt24411 daysjulia> dt2 - dt-4411 daysjulia> dt = DateTime(2012,2,29)2012-02-29T00:00:00julia> dt2 = DateTime(2000,2,1)2000-02-01T00:00:00julia> dt - dt2381110400000 milliseconds

Accessor Functions

Because theDate andDateTime types are stored as singleInt64 values, date parts or fields can be retrieved through accessor functions. The lowercase accessors return the field as an integer:

julia> t = Date(2014, 1, 31)2014-01-31julia> Dates.year(t)2014julia> Dates.month(t)1julia> Dates.week(t)5julia> Dates.day(t)31

While propercase return the same value in the correspondingPeriod type:

julia> Dates.Year(t)2014 yearsjulia> Dates.Day(t)31 days

Compound methods are provided because it is more efficient to access multiple fields at the same time than individually:

julia> Dates.yearmonth(t)(2014, 1)julia> Dates.monthday(t)(1, 31)julia> Dates.yearmonthday(t)(2014, 1, 31)

One may also access the underlyingUTInstant or integer value:

julia> dump(t)Date  instant: Dates.UTInstant{Day}    periods: Day      value: Int64 735264julia> t.instantDates.UTInstant{Day}(Day(735264))julia> Dates.value(t)735264

Query Functions

Query functions provide calendrical information about aTimeType. They include information about the day of the week:

julia> t = Date(2014, 1, 31)2014-01-31julia> Dates.dayofweek(t)5julia> Dates.dayname(t)"Friday"julia> Dates.dayofweekofmonth(t) # 5th Friday of January5

Month of the year:

julia> Dates.monthname(t)"January"julia> Dates.daysinmonth(t)31

As well as information about theTimeType's year and quarter:

julia> Dates.isleapyear(t)falsejulia> Dates.dayofyear(t)31julia> Dates.quarterofyear(t)1julia> Dates.dayofquarter(t)31

Thedayname andmonthname methods can also take an optionallocale keyword that can be used to return the name of the day or month of the year for other languages/locales. There are also versions of these functions returning the abbreviated names, namelydayabbr andmonthabbr. First the mapping is loaded into theLOCALES variable:

julia> french_months = ["janvier", "février", "mars", "avril", "mai", "juin",                        "juillet", "août", "septembre", "octobre", "novembre", "décembre"];julia> french_months_abbrev = ["janv","févr","mars","avril","mai","juin",                              "juil","août","sept","oct","nov","déc"];julia> french_days = ["lundi","mardi","mercredi","jeudi","vendredi","samedi","dimanche"];julia> Dates.LOCALES["french"] = Dates.DateLocale(french_months, french_months_abbrev, french_days, [""]);

The above mentioned functions can then be used to perform the queries:

julia> Dates.dayname(t;locale="french")"vendredi"julia> Dates.monthname(t;locale="french")"janvier"julia> Dates.monthabbr(t;locale="french")"janv"

Since the abbreviated versions of the days are not loaded, trying to use the functiondayabbr will throw an error.

julia> Dates.dayabbr(t;locale="french")ERROR: BoundsError: attempt to access 1-element Vector{String} at index [5]Stacktrace:[...]

TimeType-Period Arithmetic

It's good practice when using any language/date framework to be familiar with how date-period arithmetic is handled as there are sometricky issues to deal with (though much less so for day-precision types).

TheDates module approach tries to follow the simple principle of trying to change as little as possible when doingPeriod arithmetic. This approach is also often known ascalendrical arithmetic or what you would probably guess if someone were to ask you the same calculation in a conversation. Why all the fuss about this? Let's take a classic example: add 1 month to January 31st, 2014. What's the answer? Javascript will sayMarch 3 (assumes 31 days). PHP saysMarch 2 (assumes 30 days). The fact is, there is no right answer. In theDates module, it gives the result of February 28th. How does it figure that out? Consider the classic 7-7-7 gambling game in casinos.

Now just imagine that instead of 7-7-7, the slots are Year-Month-Day, or in our example, 2014-01-31. When you ask to add 1 month to this date, the month slot is incremented, so now we have 2014-02-31. Then the day number is checked if it is greater than the last valid day of the new month; if it is (as in the case above), the day number is adjusted down to the last valid day (28). What are the ramifications with this approach? Go ahead and add another month to our date,2014-02-28 + Month(1) == 2014-03-28. What? Were you expecting the last day of March? Nope, sorry, remember the 7-7-7 slots. As few slots as possible are going to change, so we first increment the month slot by 1, 2014-03-28, and boom, we're done because that's a valid date. On the other hand, if we were to add 2 months to our original date, 2014-01-31, then we end up with 2014-03-31, as expected. The other ramification of this approach is a loss in associativity when a specific ordering is forced (i.e. adding things in different orders results in different outcomes). For example:

julia> (Date(2014,1,29)+Dates.Day(1)) + Dates.Month(1)2014-02-28julia> (Date(2014,1,29)+Dates.Month(1)) + Dates.Day(1)2014-03-01

What's going on there? In the first line, we're adding 1 day to January 29th, which results in 2014-01-30; then we add 1 month, so we get 2014-02-30, which then adjusts down to 2014-02-28. In the second example, we add 1 monthfirst, where we get 2014-02-29, which adjusts down to 2014-02-28, andthen add 1 day, which results in 2014-03-01. One design principle that helps in this case is that, in the presence of multiple Periods, the operations will be ordered by the Periods'types, not their value or positional order; this meansYear will always be added first, thenMonth, thenWeek, etc. Hence the followingdoes result in associativity and Just Works:

julia> Date(2014,1,29) + Dates.Day(1) + Dates.Month(1)2014-03-01julia> Date(2014,1,29) + Dates.Month(1) + Dates.Day(1)2014-03-01

Tricky? Perhaps. What is an innocentDates user to do? The bottom line is to be aware that explicitly forcing a certain associativity, when dealing with months, may lead to some unexpected results, but otherwise, everything should work as expected. Thankfully, that's pretty much the extent of the odd cases in date-period arithmetic when dealing with time in UT (avoiding the "joys" of dealing with daylight savings, leap seconds, etc.).

As a bonus, all period arithmetic objects work directly with ranges:

julia> dr = Date(2014,1,29):Day(1):Date(2014,2,3)Date("2014-01-29"):Day(1):Date("2014-02-03")julia> collect(dr)6-element Vector{Date}: 2014-01-29 2014-01-30 2014-01-31 2014-02-01 2014-02-02 2014-02-03julia> dr = Date(2014,1,29):Dates.Month(1):Date(2014,07,29)Date("2014-01-29"):Month(1):Date("2014-07-29")julia> collect(dr)7-element Vector{Date}: 2014-01-29 2014-02-28 2014-03-29 2014-04-29 2014-05-29 2014-06-29 2014-07-29

Adjuster Functions

As convenient as date-period arithmetic is, often the kinds of calculations needed on dates take on acalendrical ortemporal nature rather than a fixed number of periods. Holidays are a perfect example; most follow rules such as "Memorial Day = Last Monday of May", or "Thanksgiving = 4th Thursday of November". These kinds of temporal expressions deal with rules relative to the calendar, like first or last of the month, next Tuesday, or the first and third Wednesdays, etc.

TheDates module provides theadjuster API through several convenient methods that aid in simply and succinctly expressing temporal rules. The first group of adjuster methods deal with the first and last of weeks, months, quarters, and years. They each take a singleTimeType as input and return oradjust to the first or last of the desired period relative to the input.

julia> Dates.firstdayofweek(Date(2014,7,16)) # Adjusts the input to the Monday of the input's week2014-07-14julia> Dates.lastdayofmonth(Date(2014,7,16)) # Adjusts to the last day of the input's month2014-07-31julia> Dates.lastdayofquarter(Date(2014,7,16)) # Adjusts to the last day of the input's quarter2014-09-30

The next two higher-order methods,tonext, andtoprev, generalize working with temporal expressions by taking aDateFunction as first argument, along with a startingTimeType. ADateFunction is just a function, usually anonymous, that takes a singleTimeType as input and returns aBool,true indicating a satisfied adjustment criterion. For example:

julia> istuesday = x->Dates.dayofweek(x) == Dates.Tuesday; # Returns true if the day of the week of x is Tuesdayjulia> Dates.tonext(istuesday, Date(2014,7,13)) # 2014-07-13 is a Sunday2014-07-15julia> Dates.tonext(Date(2014,7,13), Dates.Tuesday) # Convenience method provided for day of the week adjustments2014-07-15

This is useful with the do-block syntax for more complex temporal expressions:

julia> Dates.tonext(Date(2014,7,13)) do x           # Return true on the 4th Thursday of November (Thanksgiving)           Dates.dayofweek(x) == Dates.Thursday &&           Dates.dayofweekofmonth(x) == 4 &&           Dates.month(x) == Dates.November       end2014-11-27

TheBase.filter method can be used to obtain all valid dates/moments in a specified range:

# Pittsburgh street cleaning; Every 2nd Tuesday from April to November# Date range from January 1st, 2014 to January 1st, 2015julia> dr = Dates.Date(2014):Day(1):Dates.Date(2015);julia> filter(dr) do x           Dates.dayofweek(x) == Dates.Tue &&           Dates.April <= Dates.month(x) <= Dates.Nov &&           Dates.dayofweekofmonth(x) == 2       end8-element Vector{Date}: 2014-04-08 2014-05-13 2014-06-10 2014-07-08 2014-08-12 2014-09-09 2014-10-14 2014-11-11

Additional examples and tests are available instdlib/Dates/test/adjusters.jl.

Period Types

Periods are a human view of discrete, sometimes irregular durations of time. Consider 1 month; it could represent, in days, a value of 28, 29, 30, or 31 depending on the year and month context. Or a year could represent 365 or 366 days in the case of a leap year.Period types are simpleInt64 wrappers and are constructed by wrapping anyInt64 convertible type, i.e.Year(1) orMonth(3.0). Arithmetic betweenPeriod of the same type behave like integers, and limitedPeriod-Real arithmetic is available. You can extract the underlying integer withDates.value.

julia> y1 = Dates.Year(1)1 yearjulia> y2 = Dates.Year(2)2 yearsjulia> y3 = Dates.Year(10)10 yearsjulia> y1 + y23 yearsjulia> div(y3,y2)5julia> y3 - y28 yearsjulia> y3 % y20 yearsjulia> div(y3,3) # mirrors integer division3 yearsjulia> Dates.value(Dates.Millisecond(10))10

Representing periods or durations that are not integer multiples of the basic types can be achieved with theDates.CompoundPeriod type. Compound periods may be constructed manually from simplePeriod types. Additionally, thecanonicalize function can be used to break down a period into aDates.CompoundPeriod. This is particularly useful to convert a duration, e.g., a difference of twoDateTime, into a more convenient representation.

julia> cp = Dates.CompoundPeriod(Day(1),Minute(1))1 day, 1 minutejulia> t1 = DateTime(2018,8,8,16,58,00)2018-08-08T16:58:00julia> t2 = DateTime(2021,6,23,10,00,00)2021-06-23T10:00:00julia> canonicalize(t2-t1) # creates a CompoundPeriod149 weeks, 6 days, 17 hours, 2 minutes

Rounding

Date andDateTime values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) withfloor,ceil, orround:

julia> floor(Date(1985, 8, 16), Dates.Month)1985-08-01julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Dates.Minute(15))2013-02-13T00:45:00julia> round(DateTime(2016, 8, 6, 20, 15), Dates.Day)2016-08-07T00:00:00

Unlike the numericround method, which breaks ties toward the even number by default, theTimeTyperound method uses theRoundNearestTiesUp rounding mode. (It's difficult to guess what breaking ties to nearest "even"TimeType would entail.) Further details on the availableRoundingMode s can be found in theAPI reference.

Rounding should generally behave as expected, but there are a few cases in which the expected behaviour is not obvious.

Rounding Epoch

In many cases, the resolution specified for rounding (e.g.,Dates.Second(30)) divides evenly into the next largest period (in this case,Dates.Minute(1)). But rounding behaviour in cases in which this is not true may lead to confusion. What is the expected result of rounding aDateTime to the nearest 10 hours?

julia> round(DateTime(2016, 7, 17, 11, 55), Dates.Hour(10))2016-07-17T12:00:00

That may seem confusing, given that the hour (12) is not divisible by 10. The reason that2016-07-17T12:00:00 was chosen is that it is 17,676,660 hours after0000-01-01T00:00:00, and 17,676,660 is divisible by 10.

As JuliaDate andDateTime values are represented according to the ISO 8601 standard,0000-01-01T00:00:00 was chosen as base (or "rounding epoch") from which to begin the count of days (and milliseconds) used in rounding calculations. (Note that this differs slightly from Julia's internal representation ofDate s usingRata Die notation; but since the ISO 8601 standard is most visible to the end user,0000-01-01T00:00:00 was chosen as the rounding epoch instead of the0000-12-31T00:00:00 used internally to minimize confusion.)

The only exception to the use of0000-01-01T00:00:00 as the rounding epoch is when rounding to weeks. Rounding to the nearest week will always return a Monday (the first day of the week as specified by ISO 8601). For this reason, we use0000-01-03T00:00:00 (the first day of the first week of year 0000, as defined by ISO 8601) as the base when rounding to a number of weeks.

Here is a related case in which the expected behaviour is not necessarily obvious: What happens when we round to the nearestP(2), whereP is aPeriod type? In some cases (specifically, whenP <: Dates.TimePeriod) the answer is clear:

julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Hour(2))2016-07-17T08:00:00julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Minute(2))2016-07-17T08:56:00

This seems obvious, because two of each of these periods still divides evenly into the next larger order period. But in the case of two months (which still divides evenly into one year), the answer may be surprising:

julia> round(DateTime(2016, 7, 17, 8, 55, 30), Dates.Month(2))2016-07-01T00:00:00

Why round to the first day in July, even though it is month 7 (an odd number)? The key is that months are 1-indexed (the first month is assigned 1), unlike hours, minutes, seconds, and milliseconds (the first of which are assigned 0).

This means that rounding aDateTime to an even multiple of seconds, minutes, hours, or years (because the ISO 8601 specification includes a year zero) will result in aDateTime with an even value in that field, while rounding aDateTime to an even multiple of months will result in the months field having an odd value. Because both months and years may contain an irregular number of days, whether rounding to an even number of days will result in an even value in the days field is uncertain.

See theAPI reference for additional information on methods exported from theDates module.

API reference

Dates and Time Types

Dates.PeriodType
PeriodYearQuarterMonthWeekDayHourMinuteSecondMillisecondMicrosecondNanosecond

Period types represent discrete, human representations of time.

Dates.CompoundPeriodType
CompoundPeriod

ACompoundPeriod is useful for expressing time periods that are not a fixed multiple of smaller periods. For example, "a year and a day" is not a fixed number of days, but can be expressed using aCompoundPeriod. In fact, aCompoundPeriod is automatically generated by addition of different period types, e.g.Year(1) + Day(1) produces aCompoundPeriod result.

Dates.InstantType
Instant

Instant types represent integer-based, machine representations of time as continuous timelines starting from an epoch.

Dates.UTInstantType
UTInstant{T}

TheUTInstant represents a machine timeline based on UT time (1 day = one revolution of the earth). TheT is aPeriod parameter that indicates the resolution or precision of the instant.

Dates.TimeTypeType
TimeType

TimeType types wrapInstant machine instances to provide human representations of the machine instant.Time,DateTime andDate are subtypes ofTimeType.

Dates.DateTimeType
DateTime

DateTime represents a point in time according to the proleptic Gregorian calendar. The finest resolution of the time is millisecond (i.e., microseconds or nanoseconds cannot be represented by this type). The type supports fixed-point arithmetic, and thus is prone to underflowing (and overflowing). A notable consequence is rounding when adding aMicrosecond or aNanosecond:

julia> dt = DateTime(2023, 8, 19, 17, 45, 32, 900)2023-08-19T17:45:32.900julia> dt + Millisecond(1)2023-08-19T17:45:32.901julia> dt + Microsecond(1000) # 1000us == 1ms2023-08-19T17:45:32.901julia> dt + Microsecond(999) # 999us rounded to 1000us2023-08-19T17:45:32.901julia> dt + Microsecond(1499) # 1499 rounded to 1000us2023-08-19T17:45:32.901
Dates.DateType
Date

Date wraps aUTInstant{Day} and interprets it according to the proleptic Gregorian calendar.

Dates.TimeType
Time

Time wraps aNanosecond and represents a specific moment in a 24-hour day.

Dates.TimeZoneType
TimeZone

Geographic zone generally based on longitude determining what the time is at a certain location. Some time zones observe daylight savings (eg EST -> EDT). For implementations and more support, see theTimeZones.jl package

Dates.UTCType
UTC

UTC, or Coordinated Universal Time, is theTimeZone from which all others are measured. It is associated with the time at 0° longitude. It is not adjusted for daylight savings.

Dates Functions

Dates.DateTimeMethod
DateTime(y, [m, d, h, mi, s, ms]) -> DateTime

Construct aDateTime type by parts. Arguments must be convertible toInt64.

Dates.DateTimeMethod
DateTime(periods::Period...) -> DateTime

Construct aDateTime type byPeriod type parts. Arguments may be in any order. DateTime parts not provided will default to the value ofDates.default(period).

Dates.DateTimeMethod
DateTime(f::Function, y[, m, d, h, mi, s]; step=Day(1), limit=10000) -> DateTime

Create aDateTime through the adjuster API. The starting point will be constructed from the providedy, m, d... arguments, and will be adjusted untilf::Function returnstrue. The step size in adjusting can be provided manually through thestep keyword.limit provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case thatf::Function is never satisfied).

Examples

julia> DateTime(dt -> second(dt) == 40, 2010, 10, 20, 10; step = Second(1))2010-10-20T10:00:40julia> DateTime(dt -> hour(dt) == 20, 2010, 10, 20, 10; step = Hour(1), limit = 5)ERROR: ArgumentError: Adjustment limit reached: 5 iterationsStacktrace:[...]
Dates.DateTimeMethod
DateTime(dt::Date) -> DateTime

Convert aDate to aDateTime. The hour, minute, second, and millisecond parts of the newDateTime are assumed to be zero.

Dates.DateTimeMethod
DateTime(dt::AbstractString, format::AbstractString; locale="english") -> DateTime

Construct aDateTime by parsing thedt date time string following the pattern given in theformat string (seeDateFormat for syntax).

Note

This method creates aDateFormat object each time it is called. It is recommended that you create aDateFormat object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.

Examples

julia> DateTime("2020-01-01", "yyyy-mm-dd")2020-01-01T00:00:00julia> a = ("2020-01-01", "2020-01-02");julia> [DateTime(d, dateformat"yyyy-mm-dd") for d ∈ a] # preferred2-element Vector{DateTime}: 2020-01-01T00:00:00 2020-01-02T00:00:00
Dates.formatMethod
format(dt::TimeType, format::AbstractString; locale="english") -> AbstractString

Construct a string by using aTimeType object and applying the providedformat. The following character codes can be used to construct theformat string:

CodeExamplesComment
y6Numeric year with a fixed width
Y1996Numeric year with a minimum width
m1, 12Numeric month with a minimum width
uJanMonth name shortened to 3-chars according to thelocale
UJanuaryFull month name according to thelocale keyword
d1, 31Day of the month with a minimum width
H0, 23Hour (24-hour clock) with a minimum width
M0, 59Minute with a minimum width
S0, 59Second with a minimum width
s000, 500Millisecond with a minimum width of 3
eMon, TueAbbreviated days of the week
EMondayFull day of week name

The number of sequential code characters indicate the width of the code. A format ofyyyy-mm specifies that the codey should have a width of four whilem a width of two. Codes that yield numeric digits have an associated mode: fixed-width or minimum-width. The fixed-width mode left-pads the value with zeros when it is shorter than the specified width and truncates the value when longer. Minimum-width mode works the same as fixed-width except that it does not truncate values longer than the width.

When creating aformat you can use any non-code characters as a separator. For example to generate the string "1996-01-15T00:00:00" you could useformat: "yyyy-mm-ddTHH:MM:SS". Note that if you need to use a code character as a literal you can use the escape character backslash. The string "1996y01m" can be produced with the format "yyyy\ymm\m".

Dates.DateFormatType
DateFormat(format::AbstractString, locale="english") -> DateFormat

Construct a date formatting object that can be used for parsing date strings or formatting a date object as a string. The following character codes can be used to construct theformat string:

CodeMatchesComment
Y1996, 96Returns year of 1996, 0096
y1996, 96Same asY onparse but discards excess digits onformat
m1, 01Matches 1 or 2-digit months
uJanMatches abbreviated months according to thelocale keyword
UJanuaryMatches full month names according to thelocale keyword
d1, 01Matches 1 or 2-digit days
H00Matches hours (24-hour clock)
I00For outputting hours with 12-hour clock
M00Matches minutes
S00Matches seconds
s.500Matches milliseconds
eMon, TuesMatches abbreviated days of the week
EMondayMatches full name days of the week
pAMMatches AM/PM (case-insensitive)
yyyymmdd19960101Matches fixed-width year, month, and day

Characters not listed above are normally treated as delimiters between date and time slots. For example adt string of "1996-01-15T00:00:00.0" would have aformat string like "y-m-dTH:M:S.s". If you need to use a code character as a delimiter you can escape it using backslash. The date "1995y01m" would have the format "y\ym\m".

Note that 12:00AM corresponds 00:00 (midnight), and 12:00PM corresponds to 12:00 (noon). When parsing a time with ap specifier, any hour (eitherH orI) is interpreted as as a 12-hour clock, so theI code is mainly useful for output.

Creating a DateFormat object is expensive. Whenever possible, create it once and use it many times or try thedateformat"" string macro. Using this macro creates the DateFormat object once at macro expansion time and reuses it later. There are also severalpre-defined formatters, listed later.

SeeDateTime andformat for how to use a DateFormat object to parse and write Date strings respectively.

Dates.@dateformat_strMacro
dateformat"Y-m-d H:M:S"

Create aDateFormat object. Similar toDateFormat("Y-m-d H:M:S") but creates the DateFormat object once during macro expansion.

SeeDateFormat for details about format specifiers.

Dates.DateTimeMethod
DateTime(dt::AbstractString, df::DateFormat=ISODateTimeFormat) -> DateTime

Construct aDateTime by parsing thedt date time string following the pattern given in theDateFormat object, or dateformat"yyyy-mm-dd\THH:MM:SS.s" if omitted.

Similar toDateTime(::AbstractString, ::AbstractString) but more efficient when repeatedly parsing similarly formatted date time strings with a pre-createdDateFormat object.

Dates.DateMethod
Date(y, [m, d]) -> Date

Construct aDate type by parts. Arguments must be convertible toInt64.

Dates.DateMethod
Date(period::Period...) -> Date

Construct aDate type byPeriod type parts. Arguments may be in any order.Date parts not provided will default to the value ofDates.default(period).

Dates.DateMethod
Date(f::Function, y[, m, d]; step=Day(1), limit=10000) -> Date

Create aDate through the adjuster API. The starting point will be constructed from the providedy, m, d arguments, and will be adjusted untilf::Function returnstrue. The step size in adjusting can be provided manually through thestep keyword.limit provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (given thatf::Function is never satisfied).

Examples

julia> Date(date -> week(date) == 20, 2010, 01, 01)2010-05-17julia> Date(date -> year(date) == 2010, 2000, 01, 01)2010-01-01julia> Date(date -> month(date) == 10, 2000, 01, 01; limit = 5)ERROR: ArgumentError: Adjustment limit reached: 5 iterationsStacktrace:[...]
Dates.DateMethod
Date(dt::DateTime) -> Date

Convert aDateTime to aDate. The hour, minute, second, and millisecond parts of theDateTime are truncated, so only the year, month and day parts are used in construction.

Dates.DateMethod
Date(d::AbstractString, format::AbstractString; locale="english") -> Date

Construct aDate by parsing thed date string following the pattern given in theformat string (seeDateFormat for syntax).

Note

This method creates aDateFormat object each time it is called. It is recommended that you create aDateFormat object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.

Examples

julia> Date("2020-01-01", "yyyy-mm-dd")2020-01-01julia> a = ("2020-01-01", "2020-01-02");julia> [Date(d, dateformat"yyyy-mm-dd") for d ∈ a] # preferred2-element Vector{Date}: 2020-01-01 2020-01-02
Dates.DateMethod
Date(d::AbstractString, df::DateFormat=ISODateFormat) -> Date

Construct aDate by parsing thed date string following the pattern given in theDateFormat object, or dateformat"yyyy-mm-dd" if omitted.

Similar toDate(::AbstractString, ::AbstractString) but more efficient when repeatedly parsing similarly formatted date strings with a pre-createdDateFormat object.

Dates.TimeMethod
Time(h, [mi, s, ms, us, ns]) -> Time

Construct aTime type by parts. Arguments must be convertible toInt64.

Dates.TimeMethod
Time(period::TimePeriod...) -> Time

Construct aTime type byPeriod type parts. Arguments may be in any order.Time parts not provided will default to the value ofDates.default(period).

Dates.TimeMethod
Time(f::Function, h, mi=0; step::Period=Second(1), limit::Int=10000)Time(f::Function, h, mi, s; step::Period=Millisecond(1), limit::Int=10000)Time(f::Function, h, mi, s, ms; step::Period=Microsecond(1), limit::Int=10000)Time(f::Function, h, mi, s, ms, us; step::Period=Nanosecond(1), limit::Int=10000)

Create aTime through the adjuster API. The starting point will be constructed from the providedh, mi, s, ms, us arguments, and will be adjusted untilf::Function returnstrue. The step size in adjusting can be provided manually through thestep keyword.limit provides a limit to the max number of iterations the adjustment API will pursue before throwing an error (in the case thatf::Function is never satisfied). Note that the default step will adjust to allow for greater precision for the given arguments; i.e. if hour, minute, and second arguments are provided, the default step will beMillisecond(1) instead ofSecond(1).

Examples

julia> Time(t -> minute(t) == 30, 20)20:30:00julia> Time(t -> minute(t) == 0, 20)20:00:00julia> Time(t -> hour(t) == 10, 3; limit = 5)ERROR: ArgumentError: Adjustment limit reached: 5 iterationsStacktrace:[...]
Dates.TimeMethod
Time(dt::DateTime) -> Time

Convert aDateTime to aTime. The hour, minute, second, and millisecond parts of theDateTime are used to create the newTime. Microsecond and nanoseconds are zero by default.

Dates.TimeMethod
Time(t::AbstractString, format::AbstractString; locale="english") -> Time

Construct aTime by parsing thet time string following the pattern given in theformat string (seeDateFormat for syntax).

Note

This method creates aDateFormat object each time it is called. It is recommended that you create aDateFormat object instead and use that as the second argument to avoid performance loss when using the same format repeatedly.

Examples

julia> Time("12:34pm", "HH:MMp")12:34:00julia> a = ("12:34pm", "2:34am");julia> [Time(d, dateformat"HH:MMp") for d ∈ a] # preferred2-element Vector{Time}: 12:34:00 02:34:00
Dates.TimeMethod
Time(t::AbstractString, df::DateFormat=ISOTimeFormat) -> Time

Construct aTime by parsing thet date time string following the pattern given in theDateFormat object, or dateformat"HH:MM:SS.s" if omitted.

Similar toTime(::AbstractString, ::AbstractString) but more efficient when repeatedly parsing similarly formatted time strings with a pre-createdDateFormat object.

Dates.nowMethod
now() -> DateTime

Return aDateTime corresponding to the user's system time including the system timezone locale.

Dates.nowMethod
now(::Type{UTC}) -> DateTime

Return aDateTime corresponding to the user's system time as UTC/GMT. For other time zones, see the TimeZones.jl package.

Examples

julia> now(UTC)2023-01-04T10:52:24.864
Base.epsMethod
eps(::Type{DateTime}) -> Millisecondeps(::Type{Date}) -> Dayeps(::Type{Time}) -> Nanosecondeps(::TimeType) -> Period

Return the smallest unit value supported by theTimeType.

Examples

julia> eps(DateTime)1 millisecondjulia> eps(Date)1 dayjulia> eps(Time)1 nanosecond

Accessor Functions

Dates.yearFunction
year(dt::TimeType) -> Int64

The year of aDate orDateTime as anInt64.

Dates.monthFunction
month(dt::TimeType) -> Int64

The month of aDate orDateTime as anInt64.

Dates.weekFunction
week(dt::TimeType) -> Int64

Return theISO week date of aDate orDateTime as anInt64. Note that the first week of a year is the week that contains the first Thursday of the year, which can result in dates prior to January 4th being in the last week of the previous year. For example,week(Date(2005, 1, 1)) is the 53rd week of 2004.

Examples

julia> week(Date(1989, 6, 22))25julia> week(Date(2005, 1, 1))53julia> week(Date(2004, 12, 31))53
Dates.dayFunction
day(dt::TimeType) -> Int64

The day of month of aDate orDateTime as anInt64.

Dates.hourFunction
hour(dt::DateTime) -> Int64

The hour of day of aDateTime as anInt64.

hour(t::Time) -> Int64

The hour of aTime as anInt64.

Dates.minuteFunction
minute(dt::DateTime) -> Int64

The minute of aDateTime as anInt64.

minute(t::Time) -> Int64

The minute of aTime as anInt64.

Dates.secondFunction
second(dt::DateTime) -> Int64

The second of aDateTime as anInt64.

second(t::Time) -> Int64

The second of aTime as anInt64.

Dates.millisecondFunction
millisecond(dt::DateTime) -> Int64

The millisecond of aDateTime as anInt64.

millisecond(t::Time) -> Int64

The millisecond of aTime as anInt64.

Dates.microsecondFunction
microsecond(t::Time) -> Int64

The microsecond of aTime as anInt64.

Dates.nanosecondFunction
nanosecond(t::Time) -> Int64

The nanosecond of aTime as anInt64.

Dates.YearMethod
Year(v)

Construct aYear object with the givenv value. Input must be losslessly convertible to anInt64.

Dates.MonthMethod
Month(v)

Construct aMonth object with the givenv value. Input must be losslessly convertible to anInt64.

Dates.WeekMethod
Week(v)

Construct aWeek object with the givenv value. Input must be losslessly convertible to anInt64.

Dates.DayMethod
Day(v)

Construct aDay object with the givenv value. Input must be losslessly convertible to anInt64.

Dates.HourMethod
Hour(dt::DateTime) -> Hour

The hour part of a DateTime as aHour.

Dates.MinuteMethod
Minute(dt::DateTime) -> Minute

The minute part of a DateTime as aMinute.

Dates.SecondMethod
Second(dt::DateTime) -> Second

The second part of a DateTime as aSecond.

Dates.MillisecondMethod
Millisecond(dt::DateTime) -> Millisecond

The millisecond part of a DateTime as aMillisecond.

Dates.MicrosecondMethod
Microsecond(dt::Time) -> Microsecond

The microsecond part of a Time as aMicrosecond.

Dates.NanosecondMethod
Nanosecond(dt::Time) -> Nanosecond

The nanosecond part of a Time as aNanosecond.

Dates.yearmonthFunction
yearmonth(dt::TimeType) -> (Int64, Int64)

Simultaneously return the year and month parts of aDate orDateTime.

Dates.monthdayFunction
monthday(dt::TimeType) -> (Int64, Int64)

Simultaneously return the month and day parts of aDate orDateTime.

Dates.yearmonthdayFunction
yearmonthday(dt::TimeType) -> (Int64, Int64, Int64)

Simultaneously return the year, month and day parts of aDate orDateTime.

Query Functions

Dates.daynameFunction
dayname(dt::TimeType; locale="english") -> Stringdayname(day::Integer; locale="english") -> String

Return the full day name corresponding to the day of the week of theDate orDateTime in the givenlocale. Also acceptsInteger.

Examples

julia> dayname(Date("2000-01-01"))"Saturday"julia> dayname(4)"Thursday"
Dates.dayabbrFunction
dayabbr(dt::TimeType; locale="english") -> Stringdayabbr(day::Integer; locale="english") -> String

Return the abbreviated name corresponding to the day of the week of theDate orDateTime in the givenlocale. Also acceptsInteger.

Examples

julia> dayabbr(Date("2000-01-01"))"Sat"julia> dayabbr(3)"Wed"
Dates.dayofweekFunction
dayofweek(dt::TimeType) -> Int64

Return the day of the week as anInt64 with1 = Monday, 2 = Tuesday, etc..

Examples

julia> dayofweek(Date("2000-01-01"))6
Dates.dayofmonthFunction
dayofmonth(dt::TimeType) -> Int64

The day of month of aDate orDateTime as anInt64.

Dates.dayofweekofmonthFunction
dayofweekofmonth(dt::TimeType) -> Int

For the day of week ofdt, return which number it is indt's month. So if the day of the week ofdt is Monday, then1 = First Monday of the month, 2 = Second Monday of the month, etc. In the range 1:5.

Examples

julia> dayofweekofmonth(Date("2000-02-01"))1julia> dayofweekofmonth(Date("2000-02-08"))2julia> dayofweekofmonth(Date("2000-02-15"))3
Dates.daysofweekinmonthFunction
daysofweekinmonth(dt::TimeType) -> Int

For the day of week ofdt, return the total number of that day of the week indt's month. Returns 4 or 5. Useful in temporal expressions for specifying the last day of a week in a month by includingdayofweekofmonth(dt) == daysofweekinmonth(dt) in the adjuster function.

Examples

julia> daysofweekinmonth(Date("2005-01-01"))5julia> daysofweekinmonth(Date("2005-01-04"))4
Dates.monthnameFunction
monthname(dt::TimeType; locale="english") -> Stringmonthname(month::Integer, locale="english") -> String

Return the full name of the month of theDate orDateTime orInteger in the givenlocale.

Examples

julia> monthname(Date("2005-01-04"))"January"julia> monthname(2)"February"
Dates.monthabbrFunction
monthabbr(dt::TimeType; locale="english") -> Stringmonthabbr(month::Integer, locale="english") -> String

Return the abbreviated month name of theDate orDateTime orInteger in the givenlocale.

Examples

julia> monthabbr(Date("2005-01-04"))"Jan"julia> monthabbr(2)"Feb"
Dates.daysinmonthFunction
daysinmonth(dt::TimeType) -> Int

Return the number of days in the month ofdt. Value will be 28, 29, 30, or 31.

Examples

julia> daysinmonth(Date("2000-01"))31julia> daysinmonth(Date("2001-02"))28julia> daysinmonth(Date("2000-02"))29
Dates.isleapyearFunction
isleapyear(dt::TimeType) -> Bool

Returntrue if the year ofdt is a leap year.

Examples

julia> isleapyear(Date("2004"))truejulia> isleapyear(Date("2005"))false
Dates.dayofyearFunction
dayofyear(dt::TimeType) -> Int

Return the day of the year fordt with January 1st being day 1.

Dates.daysinyearFunction
daysinyear(dt::TimeType) -> Int

Return 366 if the year ofdt is a leap year, otherwise return 365.

Examples

julia> daysinyear(1999)365julia> daysinyear(2000)366
Dates.quarterofyearFunction
quarterofyear(dt::TimeType) -> Int

Return the quarter thatdt resides in. Range of value is 1:4.

Dates.dayofquarterFunction
dayofquarter(dt::TimeType) -> Int

Return the day of the current quarter ofdt. Range of value is 1:92.

Adjuster Functions

Base.truncMethod
trunc(dt::TimeType, ::Type{Period}) -> TimeType

Truncates the value ofdt according to the providedPeriod type.

Examples

julia> trunc(DateTime("1996-01-01T12:30:00"), Day)1996-01-01T00:00:00
Dates.firstdayofweekFunction
firstdayofweek(dt::TimeType) -> TimeType

Adjustsdt to the Monday of its week.

Examples

julia> firstdayofweek(DateTime("1996-01-05T12:30:00"))1996-01-01T00:00:00
Dates.lastdayofweekFunction
lastdayofweek(dt::TimeType) -> TimeType

Adjustsdt to the Sunday of its week.

Examples

julia> lastdayofweek(DateTime("1996-01-05T12:30:00"))1996-01-07T00:00:00
Dates.firstdayofmonthFunction
firstdayofmonth(dt::TimeType) -> TimeType

Adjustsdt to the first day of its month.

Examples

julia> firstdayofmonth(DateTime("1996-05-20"))1996-05-01T00:00:00
Dates.lastdayofmonthFunction
lastdayofmonth(dt::TimeType) -> TimeType

Adjustsdt to the last day of its month.

Examples

julia> lastdayofmonth(DateTime("1996-05-20"))1996-05-31T00:00:00
Dates.firstdayofyearFunction
firstdayofyear(dt::TimeType) -> TimeType

Adjustsdt to the first day of its year.

Examples

julia> firstdayofyear(DateTime("1996-05-20"))1996-01-01T00:00:00
Dates.lastdayofyearFunction
lastdayofyear(dt::TimeType) -> TimeType

Adjustsdt to the last day of its year.

Examples

julia> lastdayofyear(DateTime("1996-05-20"))1996-12-31T00:00:00
Dates.firstdayofquarterFunction
firstdayofquarter(dt::TimeType) -> TimeType

Adjustsdt to the first day of its quarter.

Examples

julia> firstdayofquarter(DateTime("1996-05-20"))1996-04-01T00:00:00julia> firstdayofquarter(DateTime("1996-08-20"))1996-07-01T00:00:00
Dates.lastdayofquarterFunction
lastdayofquarter(dt::TimeType) -> TimeType

Adjustsdt to the last day of its quarter.

Examples

julia> lastdayofquarter(DateTime("1996-05-20"))1996-06-30T00:00:00julia> lastdayofquarter(DateTime("1996-08-20"))1996-09-30T00:00:00
Dates.tonextMethod
tonext(dt::TimeType, dow::Int; same::Bool=false) -> TimeType

Adjustsdt to the next day of week corresponding todow with1 = Monday, 2 = Tuesday, etc. Settingsame=true allows the currentdt to be considered as the nextdow, allowing for no adjustment to occur.

Dates.toprevMethod
toprev(dt::TimeType, dow::Int; same::Bool=false) -> TimeType

Adjustsdt to the previous day of week corresponding todow with1 = Monday, 2 = Tuesday, etc. Settingsame=true allows the currentdt to be considered as the previousdow, allowing for no adjustment to occur.

Dates.tofirstFunction
tofirst(dt::TimeType, dow::Int; of=Month) -> TimeType

Adjustsdt to the firstdow of its month. Alternatively,of=Year will adjust to the firstdow of the year.

Dates.tolastFunction
tolast(dt::TimeType, dow::Int; of=Month) -> TimeType

Adjustsdt to the lastdow of its month. Alternatively,of=Year will adjust to the lastdow of the year.

Dates.tonextMethod
tonext(func::Function, dt::TimeType; step=Day(1), limit=10000, same=false) -> TimeType

Adjustsdt by iterating at mostlimit iterations bystep increments untilfunc returnstrue.func must take a singleTimeType argument and return aBool.same allowsdt to be considered in satisfyingfunc.

Dates.toprevMethod
toprev(func::Function, dt::TimeType; step=Day(-1), limit=10000, same=false) -> TimeType

Adjustsdt by iterating at mostlimit iterations bystep increments untilfunc returnstrue.func must take a singleTimeType argument and return aBool.same allowsdt to be considered in satisfyingfunc.

Periods

Dates.PeriodMethod
Year(v)Quarter(v)Month(v)Week(v)Day(v)Hour(v)Minute(v)Second(v)Millisecond(v)Microsecond(v)Nanosecond(v)

Construct aPeriod type with the givenv value. Input must be losslessly convertible to anInt64.

Dates.CompoundPeriodMethod
CompoundPeriod(periods) -> CompoundPeriod

Construct aCompoundPeriod from aVector ofPeriods. AllPeriods of the same type will be added together.

Examples

julia> Dates.CompoundPeriod(Dates.Hour(12), Dates.Hour(13))25 hoursjulia> Dates.CompoundPeriod(Dates.Hour(-1), Dates.Minute(1))-1 hour, 1 minutejulia> Dates.CompoundPeriod(Dates.Month(1), Dates.Week(-2))1 month, -2 weeksjulia> Dates.CompoundPeriod(Dates.Minute(50000))50000 minutes
Dates.canonicalizeFunction
canonicalize(::CompoundPeriod) -> CompoundPeriod

Reduces theCompoundPeriod into its canonical form by applying the following rules:

  • AnyPeriod large enough be partially representable by a coarserPeriod will be broken into multiplePeriods (eg.Hour(30) becomesDay(1) + Hour(6))
  • Periods with opposite signs will be combined when possible (eg.Hour(1) - Day(1) becomes-Hour(23))

Examples

julia> canonicalize(Dates.CompoundPeriod(Dates.Hour(12), Dates.Hour(13)))1 day, 1 hourjulia> canonicalize(Dates.CompoundPeriod(Dates.Hour(-1), Dates.Minute(1)))-59 minutesjulia> canonicalize(Dates.CompoundPeriod(Dates.Month(1), Dates.Week(-2)))1 month, -2 weeksjulia> canonicalize(Dates.CompoundPeriod(Dates.Minute(50000)))4 weeks, 6 days, 17 hours, 20 minutes
Dates.valueFunction
Dates.value(x::Period) -> Int64

For a given period, return the value associated with that period. For example,value(Millisecond(10)) returns 10 as an integer.

Dates.defaultFunction
default(p::Period) -> Period

Return a sensible "default" value for the input Period by returningT(1) for Year, Month, and Day, andT(0) for Hour, Minute, Second, and Millisecond.

Dates.periodsFunction
Dates.periods(::CompoundPeriod) -> Vector{Period}

Return theVector ofPeriods that comprise the givenCompoundPeriod.

Julia 1.7

This function requires Julia 1.7 or later.

Rounding Functions

Date andDateTime values can be rounded to a specified resolution (e.g., 1 month or 15 minutes) withfloor,ceil, orround.

Base.floorMethod
floor(dt::TimeType, p::Period) -> TimeType

Return the nearestDate orDateTime less than or equal todt at resolutionp.

For convenience,p may be a type instead of a value:floor(dt, Dates.Hour) is a shortcut forfloor(dt, Dates.Hour(1)).

julia> floor(Date(1985, 8, 16), Month)1985-08-01julia> floor(DateTime(2013, 2, 13, 0, 31, 20), Minute(15))2013-02-13T00:30:00julia> floor(DateTime(2016, 8, 6, 12, 0, 0), Day)2016-08-06T00:00:00
Base.ceilMethod
ceil(dt::TimeType, p::Period) -> TimeType

Return the nearestDate orDateTime greater than or equal todt at resolutionp.

For convenience,p may be a type instead of a value:ceil(dt, Dates.Hour) is a shortcut forceil(dt, Dates.Hour(1)).

julia> ceil(Date(1985, 8, 16), Month)1985-09-01julia> ceil(DateTime(2013, 2, 13, 0, 31, 20), Minute(15))2013-02-13T00:45:00julia> ceil(DateTime(2016, 8, 6, 12, 0, 0), Day)2016-08-07T00:00:00
Base.roundMethod
round(dt::TimeType, p::Period, [r::RoundingMode]) -> TimeType

Return theDate orDateTime nearest todt at resolutionp. By default (RoundNearestTiesUp), ties (e.g., rounding 9:30 to the nearest hour) will be rounded up.

For convenience,p may be a type instead of a value:round(dt, Dates.Hour) is a shortcut forround(dt, Dates.Hour(1)).

julia> round(Date(1985, 8, 16), Month)1985-08-01julia> round(DateTime(2013, 2, 13, 0, 31, 20), Minute(15))2013-02-13T00:30:00julia> round(DateTime(2016, 8, 6, 12, 0, 0), Day)2016-08-07T00:00:00

Valid rounding modes forround(::TimeType, ::Period, ::RoundingMode) areRoundNearestTiesUp (default),RoundDown (floor), andRoundUp (ceil).

MostPeriod values can also be rounded to a specified resolution:

Base.floorMethod
floor(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> T

Roundx down to the nearest multiple ofprecision. Ifx andprecision are different subtypes ofPeriod, the return value will have the same type asprecision.

For convenience,precision may be a type instead of a value:floor(x, Dates.Hour) is a shortcut forfloor(x, Dates.Hour(1)).

julia> floor(Day(16), Week)2 weeksjulia> floor(Minute(44), Minute(15))30 minutesjulia> floor(Hour(36), Day)1 day

Rounding to aprecision ofMonths orYears is not supported, as thesePeriods are of inconsistent length.

Base.ceilMethod
ceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> T

Roundx up to the nearest multiple ofprecision. Ifx andprecision are different subtypes ofPeriod, the return value will have the same type asprecision.

For convenience,precision may be a type instead of a value:ceil(x, Dates.Hour) is a shortcut forceil(x, Dates.Hour(1)).

julia> ceil(Day(16), Week)3 weeksjulia> ceil(Minute(44), Minute(15))45 minutesjulia> ceil(Hour(36), Day)2 days

Rounding to aprecision ofMonths orYears is not supported, as thesePeriods are of inconsistent length.

Base.roundMethod
round(x::Period, precision::T, [r::RoundingMode]) where T <: Union{TimePeriod, Week, Day} -> T

Roundx to the nearest multiple ofprecision. Ifx andprecision are different subtypes ofPeriod, the return value will have the same type asprecision. By default (RoundNearestTiesUp), ties (e.g., rounding 90 minutes to the nearest hour) will be rounded up.

For convenience,precision may be a type instead of a value:round(x, Dates.Hour) is a shortcut forround(x, Dates.Hour(1)).

julia> round(Day(16), Week)2 weeksjulia> round(Minute(44), Minute(15))45 minutesjulia> round(Hour(36), Day)2 days

Valid rounding modes forround(::Period, ::T, ::RoundingMode) areRoundNearestTiesUp (default),RoundDown (floor), andRoundUp (ceil).

Rounding to aprecision ofMonths orYears is not supported, as thesePeriods are of inconsistent length.

The following functions are not exported:

Dates.floorceilFunction
floorceil(dt::TimeType, p::Period) -> (TimeType, TimeType)

Simultaneously return thefloor andceil of aDate orDateTime at resolutionp. More efficient than calling bothfloor andceil individually.

floorceil(x::Period, precision::T) where T <: Union{TimePeriod, Week, Day} -> (T, T)

Simultaneously return thefloor andceil ofPeriod at resolutionp. More efficient than calling bothfloor andceil individually.

Dates.epochdays2dateFunction
epochdays2date(days) -> Date

Take the number of days since the rounding epoch (0000-01-01T00:00:00) and return the correspondingDate.

Dates.epochms2datetimeFunction
epochms2datetime(milliseconds) -> DateTime

Take the number of milliseconds since the rounding epoch (0000-01-01T00:00:00) and return the correspondingDateTime.

Dates.date2epochdaysFunction
date2epochdays(dt::Date) -> Int64

Take the givenDate and return the number of days since the rounding epoch (0000-01-01T00:00:00) as anInt64.

Dates.datetime2epochmsFunction
datetime2epochms(dt::DateTime) -> Int64

Take the givenDateTime and return the number of milliseconds since the rounding epoch (0000-01-01T00:00:00) as anInt64.

Conversion Functions

Dates.todayFunction
today() -> Date

Return the date portion ofnow().

Dates.unix2datetimeFunction
unix2datetime(x) -> DateTime

Take the number of seconds since unix epoch1970-01-01T00:00:00 and convert to the correspondingDateTime.

Dates.datetime2unixFunction
datetime2unix(dt::DateTime) -> Float64

Take the givenDateTime and return the number of seconds since the unix epoch1970-01-01T00:00:00 as aFloat64.

Dates.julian2datetimeFunction
julian2datetime(julian_days) -> DateTime

Take the number of Julian calendar days since epoch-4713-11-24T12:00:00 and return the correspondingDateTime.

Dates.datetime2julianFunction
datetime2julian(dt::DateTime) -> Float64

Take the givenDateTime and return the number of Julian calendar days since the julian epoch-4713-11-24T12:00:00 as aFloat64.

Dates.rata2datetimeFunction
rata2datetime(days) -> DateTime

Take the number of Rata Die days since epoch0000-12-31T00:00:00 and return the correspondingDateTime.

Dates.datetime2rataFunction
datetime2rata(dt::TimeType) -> Int64

Return the number of Rata Die days since epoch from the givenDate orDateTime.

Constants

Days of the Week:

VariableAbbr.Value (Int)
MondayMon1
TuesdayTue2
WednesdayWed3
ThursdayThu4
FridayFri5
SaturdaySat6
SundaySun7

Months of the Year:

VariableAbbr.Value (Int)
JanuaryJan1
FebruaryFeb2
MarchMar3
AprilApr4
MayMay5
JuneJun6
JulyJul7
AugustAug8
SeptemberSep9
OctoberOct10
NovemberNov11
DecemberDec12

Common Date Formatters

Dates.ISODateTimeFormatConstant
Dates.ISODateTimeFormat

Describes the ISO8601 formatting for a date and time. This is the default value forDates.format of aDateTime.

Examples

julia> Dates.format(DateTime(2018, 8, 8, 12, 0, 43, 1), ISODateTimeFormat)"2018-08-08T12:00:43.001"
Dates.ISODateFormatConstant
Dates.ISODateFormat

Describes the ISO8601 formatting for a date. This is the default value forDates.format of aDate.

Examples

julia> Dates.format(Date(2018, 8, 8), ISODateFormat)"2018-08-08"
Dates.ISOTimeFormatConstant
Dates.ISOTimeFormat

Describes the ISO8601 formatting for a time. This is the default value forDates.format of aTime.

Examples

julia> Dates.format(Time(12, 0, 43, 1), ISOTimeFormat)"12:00:43.001"
Dates.RFC1123FormatConstant
Dates.RFC1123Format

Describes the RFC1123 formatting for a date and time.

Examples

julia> Dates.format(DateTime(2018, 8, 8, 12, 0, 43, 1), RFC1123Format)"Wed, 08 Aug 2018 12:00:43"
  • 1The notion of the UT second is actually quite fundamental. There are basically two different notions of time generally accepted, one based on the physical rotation of the earth (one full rotation = 1 day), the other based on the SI second (a fixed, constant value). These are radically different! Think about it, a "UT second", as defined relative to the rotation of the earth, may have a different absolute length depending on the day! Anyway, the fact thatDate andDateTime are based on UT seconds is a simplifying, yet honest assumption so that things like leap seconds and all their complexity can be avoided. This basis of time is formally calledUT or UT1. Basing types on the UT second basically means that every minute has 60 seconds and every day has 24 hours and leads to more natural calculations when working with calendar dates.

Settings


This document was generated withDocumenter.jl version 1.8.0 onWednesday 9 July 2025. Using Julia version 1.11.6.


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