Return local beginning of day time object

Question

To get a local beginning of today time object I extract YMD and reconstruct the new date. That looks like a kludge. Do I miss some other standard library function?

c

Answer 1

EDIT: This only works for UTC times (it was tested in the playground, so the location-specific test was probably wrong). See PeterSO's answer for issues of this solution in location-specific scenarios.

You can use the Truncate method on the date, with 24 * time.Hour as duration:

http://play.golang.org/p/zJ8s9-6Pck

func main() {
    // Test with a location works fine too
    loc, _ := time.LoadLocation("Europe/Berlin")
    t1, _ := time.ParseInLocation("2006 Jan 02 15:04:05 (MST)", "2012 Dec 07 03:15:30 (CEST)", loc)
    t2, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 07 00:00:00")
    t3, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 07 23:15:30")
    t4, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 07 23:59:59")
    t5, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 08 00:00:01")
    times := []time.Time{t1, t2, t3, t4, t5}

    for _, d := range times {
        fmt.Printf("%s\n", d.Truncate(24*time.Hour))
    }
}

To add some explanation, it works because truncate "rounds down to a multiple of" the specified duration since the zero time, and the zero time is January 1, year 1, 00:00:00. So truncating to the nearest 24-hour boundary always returns a "beginning of day".