Difference between two time.Time objects - datetime

Question

Very new to the 'Go'. Question might be basic one.
I have two time.Time objects and I want to get the difference between the two in terms of hours/minutes/seconds. Lets say:
t1 = 2016-09-09 19:09:16 +0530 IST
t2 = 2016-09-09 19:09:16 +0530 IST
In above case, since the difference is 0. It should give me 00:00:00. Consider another case:
t1 = 2016-09-14 14:12:48 +0530 IST
t2 = 2016-09-14 14:18:29 +0530 IST
In this case, difference would be 00:05:41. I looked at the https://godoc.org/time but could not make anything out of it.

Answer 1

You may use Time.Sub() to get the difference between the 2 time.Time values, result will be a value of time.Duration.
When printed, a time.Duration formats itself "intelligently":
t1 := time.Now()
t2 := t1.Add(time.Second * 341)
fmt.Println(t1)
fmt.Println(t2)
diff := t2.Sub(t1)
fmt.Println(diff)
Output:
2009-11-10 23:00:00 +0000 UTC
2009-11-10 23:05:41 +0000 UTC
5m41s
If you want the time format HH:mm:ss, you may constuct a time.Time value and use its Time.Format() method like this:
out := time.Time{}.Add(diff)
fmt.Println(out.Format("15:04:05"))
Output:
00:05:41
Try the examples on the Go Playground.
Of course this will only work if the time difference is less than a day. If the difference may be bigger, then it's another story. The result must include days, months and years. Complexity increases significnatly. See this question for details:
golang time.Since() with months and years
The solution presented there solves this issue by showing a function with signature:
func diff(a, b time.Time) (year, month, day, hour, min, sec int)
You may use that even if your times are within 24 hours (in which case year, month and day will be 0).

Answer 2

Actually, the time package's documentation does discuss it:
https://godoc.org/time#Time.Sub
https://godoc.org/time#Duration.Hours
You should produce a Duration object using Sub() and then use one of the Seconds(), Minutes(), Hours().
package main
import (
"fmt"
"time"
)
func main() {
t1 := time.Date(1984, time.November, 3, 13, 0, 0, 0, time.UTC)
t2 := time.Date(1984, time.November, 3, 10, 0, 0, 0, time.UTC)
fmt.Printf("The hours difference is: %f", t1.Sub(t2).Hours())
}

Answer 3

To complement Shmulik Klein's answer:
Another way to calculate disjoint hours/minutes/seconds out of a time.Duration:
https://play.golang.org/p/VRoXG5NxLo
package main
import (
"fmt"
"math"
"time"
)
func main() {
t1 := time.Date(1984, time.November, 3, 13, 0, 0, 0, time.UTC)
t2 := time.Date(1984, time.November, 3, 10, 23, 34, 0, time.UTC)
hs := t1.Sub(t2).Hours()
hs, mf := math.Modf(hs)
ms := mf * 60
ms, sf := math.Modf(ms)
ss := sf * 60
fmt.Println(hs, "hours", ms, "minutes", ss, "seconds")
}
2 hours 36 minutes 25.999999999999375 seconds
note:
slight precision loss due to the use of the float64 type
we ignore leap seconds and assume every minute has 60 seconds

Answer 4

There are 2 common ways:
straight forward one:
startTime := time.Now()
diff := time.Now().Sub(startTime)
shorter one (a bit):
startTime := time.Now()
diff := time.Since(startTime)

Answer 5

DEMO
package main
import (
"fmt"
"math"
"time"
)
func TimeAsString(dt float64) string {
time := dt
hours := math.Floor(time / 3600)
minutes := math.Ceil(math.Mod(time, 3600)/60) - 1
seconds := int(time) % 60
return fmt.Sprintf("%v:%v:%v", hours, minutes, seconds)
}
func main() {
mytime := 0.0
last := time.Now()
tick := time.Tick(33 * time.Millisecond)
for {
select {
case <-tick:
dt := time.Since(last).Seconds()
last = time.Now()
mytime += dt
fmt.Println(TimeAsString(mytime))
}
}
}