time.Time Round to Day - go

Question

I have a timestamp coming in, I wonder if there's a way to round it down to the start of a day in PST. For example, ts: 1305861602 corresponds to 2016-04-14, 21:10:27 -0700, but I want to round it to a timestamp that maps to 2016-04-14 00:00:00 -0700. I read through the time.Time doc but didn't find a way to do it.

Answer 1

The simple way to do this is to create new Time using the previous one and only assigning the year month and day. It would look like this;
func truncateToDay(t time.Time) time.Time {
return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
}
here's a play example; https://play.golang.org/p/jnFuZxruKm

Answer 2

You can simply use duration 24 * time.Hour to truncate time.
t := time.Date(2015, 4, 2, 0, 15, 30, 918273645, time.UTC)
d := 24 * time.Hour
t.Truncate(d)
https://play.golang.org/p/BTz7wjLTWX

Answer 3

I believe the simplest is to create a new date as shown in this answer.
However, if you wanna use time.Truncate, there is two distinct cases.
If you are working in UTC:
var testUtcTime = time.Date(2016, 4, 14, 21, 10, 27, 0, time.UTC)
// outputs 2016-04-14T00:00:00Z
fmt.Println(testUtcTime.Truncate(time.Hour * 24).Format(time.RFC3339))
If you are not, you need to convert back and forth to UTC
var testTime = time.Date(2016, 4, 14, 21, 10, 27, 0, time.FixedZone("my zone", -7*3600))
// this is wrong (outputs 2016-04-14T17:00:00-07:00)
fmt.Println(testTime.Truncate(time.Hour * 24).Format(time.RFC3339))
// this is correct (outputs 2016-04-14T00:00:00-07:00)
fmt.Println(testTime.Add(-7 * 3600 * time.Second).Truncate(time.Hour * 24).Add(7 * 3600 * time.Second).Format(time.RFC3339))

Answer 4

in addition to sticky's answer to get the local Truncate do like this
t := time.Date(2015, 4, 2, 0, 15, 30, 918273645, time.Local)
d := 24 * time.Hour

fmt.Println("in UTC", t.Truncate(d))
_, dif := t.Zone()
fmt.Println("in Local", t.Truncate(24 * time.Hour).Add(time.Second * time.Duration(-dif)))

Answer 5

func truncateToDay(t time.Time) {
nt, _ := time.Parse("2006-01-02", t.Format("2006-01-02"))
fmt.Println(nt)
}
This is not elegant but works.

Answer 6

I using theses functions on all my projects:
package time_utils
import "time"
func TruncateToStartOfDay(t time.Time) time.Time {
return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
}
func TruncateToEndOfDay(t time.Time) time.Time {
return time.Date(t.Year(), t.Month(), t.Day(), 23, 59, 59, 0, t.Location())
}