Subtracting time.Duration from time in Go

I have a time.Time value obtained from time.Now() and I want to get another time which is exactly 1 month ago.

I know subtracting is possible with time.Sub() (which wants another time.Time), but that will result in a time.Duration and I need it the other way around.

4 Answers

In response to Thomas Browne's comment, because lnmx's answer only works for subtracting a date, here is a modification of his code that works for subtracting time from a time.Time type.

package main import ( "fmt" "time" ) func main() { now := time.Now() fmt.Println("now:", now) count := 10 then := now.Add(time.Duration(-count) * time.Minute) // if we had fix number of units to subtract, we can use following line instead fo above 2 lines. It does type convertion automatically. // then := now.Add(-10 * time.Minute) fmt.Println("10 minutes ago:", then) } 

Produces:

now: 2009-11-10 23:00:00 +0000 UTC 10 minutes ago: 2009-11-10 22:50:00 +0000 UTC 

Not to mention, you can also use time.Hour or time.Second instead of time.Minute as per your needs.

Playground:

Try AddDate:

package main import ( "fmt" "time" ) func main() { now := time.Now() fmt.Println("now:", now) then := now.AddDate(0, -1, 0) fmt.Println("then:", then) } 

Produces:

now: 2009-11-10 23:00:00 +0000 UTC then: 2009-10-10 23:00:00 +0000 UTC 

Playground:

You can negate a time.Duration:

then := now.Add(- dur) 

You can even compare a time.Duration against 0:

if dur > 0 { dur = - dur } then := now.Add(dur) 

You can see a working example at

There's time.ParseDuration which will happily accept negative durations, as per manual. Otherwise put, there's no need to negate a duration where you can get an exact duration in the first place.

E.g. when you need to substract an hour and a half, you can do that like so:

package main import ( "fmt" "time" ) func main() { now := time.Now() fmt.Println("now:", now) duration, _ := time.ParseDuration("-1.5h") then := now.Add(duration) fmt.Println("then:", then) }