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The Way to Go

Times and Dates

Explore the Go time package to manipulate dates and times effectively. Learn to get current time, format dates in custom styles, work with durations and time zones, and measure elapsed time for better application control.

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The time Package

The package time gives us a datatype Time (to be used as a value) and functionality for displaying and measuring time and dates. The current time is given by time.Now(), and the parts of a time can then be obtained as t.Day(), t.Minute(), and so on. You can make your own time-formats as in:

t := time.Now()
fmt.Printf("%02d.%02d.%4d\n", t.Day(), t.Month(), t.Year()) // e.g.: 29.10.2019
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The type Duration represents the elapsed time between two instants as an int64 nanosecond count. A handy function is Since(t Time) that returns the time elapsed since t. The type Location maps time instants to the zone in use at that time. UTC represents Universal Coordinated Time. There is a predefined function Format with syntax as:

func (t Time) Format(s string) string

It formats a time t into a string according to an s string, with some predefined formats like time.ANSIC or time.RFC822. The general layout defines the format by showing the representation of a standard time, which is then used to describe the time to be formatted; this seems strange, but an example makes this clear:

t := time.Now().UTC()
fmt.Println(t.Format("02 Jan 2006 15:04"))// e.g: 29 Oct 2019 11:00

Run the following program to see how the above-discussed functionalities work.

Go (1.6.2)
package main
import (
"fmt"
"time"
)
var week time.Duration
func main() {
    t := time.Now()
    fmt.Println(t)
    fmt.Printf("%02d.%02d.%4d\n", t.Day(), t.Month(), t.Year())
    t = time.Now().UTC()
    fmt.Println(t)
    fmt.Println(time.Now())
    // calculating times:
    week = 60 * 60 * 24 * 7 * 1e9 // must be in nanosec
    week_from_now := t.Add(week)
    fmt.Println(week_from_now)
    // formatting times:
    fmt.Println(t.Format(time.RFC822))
    fmt.Println(t.Format(time.ANSIC))
    fmt.Println(t.Format("02 Jan 2006 15:04"))
    s := t.Format("2006 01 02")
    fmt.Println(t, "=>", s)
}

As you can see in the above code, at line 10 we declared t time and initialized with the present time by time.Now(). Printing the t at line 11 prints complete time with default format. At line 12 we specify the format of t as dd.mm.yyyy. Next, we decide to add week in our time. We declared the week variable and initialize it with a value of (60∗60∗24∗7∗1e9)(60*60*24*7*1e9) at line 17. We multiply a factor of 1e91e9 because we have to keep it in nanoseconds. At line 18 we add week to our time t. Now after printing t, change is noticeable, as weeks are added into t. At line 21 time is printed in RFC822 format, e.g., 30 Oct 19 11:34 UTC At line 22 time is printed in ANSIC format, e.g., Wed Oct 30 11:34:03 2019. At line 23 time is printed in 02 Jan 2006 15:04 format, e.g., 30 Oct 2019 11:34. At line 24 we create a format(yyyy.mm.dd) and store it in s. In the next line, we print the time t in default format and then in the format specified above.

For more information on Golang’s time package, visit this page.

That’s about time package. In the next lesson, you’ll study pointers.