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time

By · Reviewed & last updated · Part of Go Tutorial

The time package is the right kind of opinionated: a Time is location-aware, durations are typed, and the layout-based parser is unique to Go but catches a class of formatting bugs at compile time. Default to time.Now().UTC() at the API boundary, and use time.Time for everything in between — never a string.

Parse, format, compare, schedule, and benchmark

EXAMPLE
package main

import (
	"fmt"
	"time"
)

func main() {
	// 1) Now, UTC, and the local zone
	now := time.Now()
	fmt.Println(now)               // 2026-06-11 09:30:00 +1000 AEST
	fmt.Println(now.UTC())         // 2026-06-10 23:30:00 +0000 UTC

	// 2) Parse with the famous reference layout: Mon Jan 2 15:04:05 MST 2006
	t, err := time.Parse(time.RFC3339, "2026-06-11T09:30:00+10:00")
	if err != nil { panic(err) }
	fmt.Println(t.Format("Mon 02 Jan 2006 3:04pm"))

	// 3) Durations are a real type, not a number-of-seconds-in-disguise
	timeout := 30 * time.Second
	tick    := 250 * time.Millisecond
	fmt.Println("timeout in seconds:", timeout.Seconds())

	// 4) Comparisons and arithmetic
	deadline := time.Now().Add(5 * time.Minute)
	if time.Now().Before(deadline) { fmt.Println("not yet") }
	delta := deadline.Sub(time.Now()) // returns time.Duration
	fmt.Println("delta:", delta.Round(time.Second))

	// 5) Time-zone aware: load IANA zones
	syd, _ := time.LoadLocation("Australia/Sydney")
	mumbai, _ := time.LoadLocation("Asia/Kolkata")
	standup := time.Date(2026, 6, 12, 9, 0, 0, 0, syd)
	fmt.Println("standup in Mumbai:", standup.In(mumbai))

	// 6) Tickers and timers — channel-based scheduling
	t1 := time.NewTicker(tick)
	defer t1.Stop()
	stop := time.After(2 * time.Second)
loop:
	for {
		select {
		case <-t1.C:
			fmt.Println("tick")
		case <-stop:
			break loop
		}
	}

	// 7) Benchmark a block with time.Since (no need for a separate library)
	start := time.Now()
	heavyWork()
	fmt.Println("heavyWork took", time.Since(start))

	// 8) Truncate / Round for bucketing — group events into 5-min bins
	bucket := now.Truncate(5 * time.Minute)
	fmt.Println("bucket:", bucket)

	// 9) Monotonic clock — Sub and Since use it so leap seconds and NTP
	//    adjustments do not throw off short measurements.
}

func heavyWork() { time.Sleep(100 * time.Millisecond) }

Why it matters

For wall-clock comparisons between events on different machines, always use Unix or UnixNano + clock-skew tolerance. For measuring elapsed time on one machine, use the monotonic clock via time.Since/Sub — it is immune to wall-clock jumps and NTP adjustments that would otherwise produce negative durations.

Tip: Tweak the snippet with Try it Yourself », then sit the quiz at the bottom of the page.

Example

Example
now := time.Now()
fmt.Println(now.Format("2006-01-02 15:04:05"))
Try it Yourself »

Discussion

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