Difference between two time.Time objects

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).

---

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())
}

---

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

---

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))
        }

    }
}

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