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Parse iso8601 duration strings, and use to shift dates/times.
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senseyeio/duration
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Parse ISO8601 duration strings, and use to shift dates/times.
package mainimport ("fmt""time""github.com/senseyeio/duration")funcmain() {d,_:=iso8601.ParseISO8601("P1D")today:=time.Now()tomorrow:=d.Shift(today)fmt.Println(today.Format("Jan _2"))fmt.Println(tomorrow.Format("Jan _2"))}
Why can't we just use a
time.Durationandtime.Add?
A very reasonable question.
The code below repeatedly adds 24 hours to atime.Time. You might expect the time on that date to stay the same, butthere are not always 24 hours in a day. When the clocks change in New York, the time will skew by an hour. As you can see from the output, duration.Duration.Shift() can increment the date without shifting the time.
package mainimport ("fmt""time""github.com/senseyeio/duration")funcmain() {loc,_:=time.LoadLocation("America/New_York")d,_:=iso8601.ParseISO8601("P1D")t1,_:=time.ParseInLocation("Jan 2, 2006 at 3:04pm","Jan 1, 2006 at 3:04pm",loc)t2:=t1fori:=0;i<365;i++ {t1=t1.Add(24*time.Hour)t2=d.Shift(t2)fmt.Printf("time.Add:%d Duration.Shift:%d\n",t1.Hour(),t2.Hour())}}// Outputs// time.Add:15 Duration.Shift:15// time.Add:15 Duration.Shift:15// time.Add:15 Duration.Shift:15// ...// time.Add:16 Duration.Shift:15// time.Add:16 Duration.Shift:15// time.Add:16 Duration.Shift:15// ...
Months are tricky. Shifting by months usestime.AddDate(), which is great. However, be aware of how differing days in the month are accommodated. Dates will 'roll over' if the month you're shifting to has fewer days. e.g. if you start on Jan 30th and repeat every "P1M", you'll get this:
Jan 30, 2006Mar 2, 2006Apr 2, 2006May 2, 2006Jun 2, 2006Jul 2, 2006Aug 2, 2006Sep 2, 2006Oct 2, 2006Nov 2, 2006Dec 2, 2006Jan 2, 2007