time.Now() / Sleep() / Format()

import "time"

// Gets the current local time.
t := time.Now()

// Pauses execution for the specified duration.
time.Sleep(2 * time.Second)
time.Sleep(500 * time.Millisecond)

// Formats the time as a string using the specified layout.
s := t.Format("2006-01-02 15:04:05")  // Uses Go's reference time.

// Parses a time value from a string.
t2, err := time.Parse("2006-01-02", "2026-03-05")

// Adds or subtracts a duration from a time value.
tomorrow := t.Add(24 * time.Hour)
yesterday := t.Add(-24 * time.Hour)

package main

import (
    "fmt"
    "time"
)

func main() {
    // Get the current time and extract individual fields.
    now := time.Now()
    fmt.Println("Current time:", now)
    fmt.Printf("Year=%d Month=%d Day=%d\n", now.Year(), now.Month(), now.Day())
    fmt.Printf("Hour=%d Minute=%d Second=%d\n", now.Hour(), now.Minute(), now.Second())
    fmt.Println("Unix timestamp:", now.Unix())

    fmt.Println()

    // Format the time using Go's reference time: "2006-01-02 15:04:05".
    fmt.Println("yyyy/MM/dd format:", now.Format("2006/01/02"))
    fmt.Println("Date and time:", now.Format("2006-01-02 15:04:05"))
    fmt.Println("Long format:", now.Format("January 2, 2006 15:04"))
    fmt.Println("RFC3339 format:", now.Format(time.RFC3339))

    fmt.Println()

    // Add and subtract durations.
    tomorrow := now.Add(24 * time.Hour)
    fmt.Println("Tomorrow:", tomorrow.Format("2006-01-02"))

    nextWeek := now.Add(7 * 24 * time.Hour)
    fmt.Println("Next week:", nextWeek.Format("2006-01-02"))

    fmt.Println()

    // Measure elapsed time.
    start := time.Now()
    time.Sleep(100 * time.Millisecond) // Wait 100ms.
    elapsed := time.Since(start)
    fmt.Println("Elapsed:", elapsed)

    fmt.Println()

    // Parse a time value from a string.
    t, err := time.Parse("2006-01-02", "2026-03-05")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    fmt.Println("Parsed date:", t.Format("January 2, 2006"))

    // Calculate the difference between two time values.
    diff := tomorrow.Sub(now)
    fmt.Printf("Hours from now to tomorrow: %.0f\n", diff.Hours())
}

Go's time formatting uses a unique reference time — January 2, 2006 at 15:04:05 — instead of placeholders like %Y-%m-%d used in other languages. You write your desired format by substituting that exact reference date and time. For example, "2006/01/02" produces output in YYYY/MM/DD format.

time.Duration represents a length of time. You combine constants like time.Second and time.Millisecond with multiplication. For example, two seconds is written as 2 * time.Second.

time.Sleep() blocks the current goroutine. In concurrent contexts such as servers, consider using time.After or time.Ticker instead.