Difference between two time.Time objects

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.

Solution 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).

Solution 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())
}

Solution 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