convert 12 hour format to 24 hour format time in golang

Question

In golang I have not found any way to convert 12 hour format string time to 24 hour format as below:

07:05:45PM to 19:05:45

I have tried below using layout

layout := "Mon Jan 2 15:04:05 -0700 MST 2006"
/*
 * Write your code here.
 */
//layout := "3:04PM"
t,_ := time.Parse(layout,s)
fmt.Println(t)

Output is:

07:05:45PM

I have looked for answers similar to this but it is not helping everyone is using whole layout. I found answers in another language but not in go.

Answer 1

For example,

package main

import (
    "fmt"
    "time"
)

func main() {
    layout1 := "03:04:05PM"
    layout2 := "15:04:05"
    t, err := time.Parse(layout1, "07:05:45PM")
    if err != nil {
        fmt.Println(err)
        return
    }
    fmt.Println(t.Format(layout1))
    fmt.Println(t.Format(layout2))
}

Playground: https://play.golang.org/p/Ypn2-lEF_Zs

Output:

07:05:45PM
19:05:45

---

Reference: package time

Answer 2

The key is to understand how to write the layout argument. According to godoc, the reference time for layout is:

Mon Jan 2 15:04:05 -0700 MST 2006

Each string element of a date has a specific numerical value relevant to it:

String	Represents
1 or 01 or Jan	month
2 or 02	day of month
3 or 03 or 15	hour
4 or 04	minute
5 or 05	second
6 or 06 or 2006	year
-0700 or MST	timezone representation
PM	period of day

You need to rewrite this date to your format as the layout for parse. You only need to include the elements to your need. So only the hour, minute, second and AM/PM is important. Reference time 15:04:05 should be written as 03:04:05PM.

Just use the rewritten time as the layout parameter:

import time

...


t, _ := time.Parse("03:04:05PM", "07:05:45PM")
fmt.Println(t.Format("15:04:05"))

Output:

19:05:45