@@ -2699,15 +2699,18 @@ P <optional> <replaceable>years</replaceable>-<replaceable>months</replaceable>-
26992699 </para>
27002700
27012701 <para>
2702- In the verbose input format, and in some fields of the more compact
2703- input formats, field values can have fractional parts; for example
2704- <literal>'1.5 week'</literal> or <literal>'01:02:03.45'</literal>. Such input is
2705- converted to the appropriate number of months, days, and seconds
2706- for storage. When this would result in a fractional number of
2707- months or days, the fraction is added to the lower-order fields
2708- using the conversion factors 1 month = 30 days and 1 day = 24 hours.
2709- For example, <literal>'1.5 month'</literal> becomes 1 month and 15 days.
2710- Only seconds will ever be shown as fractional on output.
2702+ Field values can have fractional parts: for example, <literal>'1.5
2703+ weeks'</literal> or <literal>'01:02:03.45'</literal>. However,
2704+ because interval internally stores only three integer units (months,
2705+ days, microseconds), fractional units must be spilled to smaller
2706+ units. Fractional parts of units greater than months is truncated to
2707+ be an integer number of months, e.g. <literal>'1.5 years'</literal>
2708+ becomes <literal>'1 year 6 mons'</literal>. Fractional parts of
2709+ weeks and days are computed to be an integer number of days and
2710+ microseconds, assuming 30 days per month and 24 hours per day, e.g.,
2711+ <literal>'1.75 months'</literal> becomes <literal>1 mon 22 days
2712+ 12:00:00</literal>. Only seconds will ever be shown as fractional
2713+ on output.
27112714 </para>
27122715
27132716 <para>
@@ -2751,10 +2754,10 @@ P <optional> <replaceable>years</replaceable>-<replaceable>months</replaceable>-
27512754
27522755 <para>
27532756 Internally <type>interval</type> values are stored as months, days,
2754- andseconds . This is done because the number of days in a month
2757+ andmicroseconds . This is done because the number of days in a month
27552758 varies, and a day can have 23 or 25 hours if a daylight savings
27562759 time adjustment is involved. The months and days fields are integers
2757- while theseconds field can storefractions . Because intervals are
2760+ while themicroseconds field can storefractional seconds . Because intervals are
27582761 usually created from constant strings or <type>timestamp</type> subtraction,
27592762 this storage method works well in most cases, but can cause unexpected
27602763 results: