src/time/example_test.go

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package time_test

import (
	"fmt"
	"time"
)

func expensiveCall() {}

func ExampleDuration() {
	t0 := time.Now()
	expensiveCall()
	t1 := time.Now()
	fmt.Printf("The call took %v to run.\n", t1.Sub(t0))
}

func ExampleDuration_Round() {
	d, err := time.ParseDuration("1h15m30.918273645s")
	if err != nil {
		panic(err)
	}

	round := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, r := range round {
		fmt.Printf("d.Round(%6s) = %s\n", r, d.Round(r).String())
	}
	// Output:
	// d.Round(   1ns) = 1h15m30.918273645s
	// d.Round(   1µs) = 1h15m30.918274s
	// d.Round(   1ms) = 1h15m30.918s
	// d.Round(    1s) = 1h15m31s
	// d.Round(    2s) = 1h15m30s
	// d.Round(  1m0s) = 1h16m0s
	// d.Round( 10m0s) = 1h20m0s
	// d.Round(1h0m0s) = 1h0m0s
}

func ExampleDuration_String() {
	t1 := time.Date(2016, time.August, 15, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2017, time.February, 16, 0, 0, 0, 0, time.UTC)
	fmt.Println(t2.Sub(t1).String())
	// Output: 4440h0m0s
}

func ExampleDuration_Truncate() {
	d, err := time.ParseDuration("1h15m30.918273645s")
	if err != nil {
		panic(err)
	}

	trunc := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, t := range trunc {
		fmt.Printf("d.Truncate(%6s) = %s\n", t, d.Truncate(t).String())
	}
	// Output:
	// d.Truncate(   1ns) = 1h15m30.918273645s
	// d.Truncate(   1µs) = 1h15m30.918273s
	// d.Truncate(   1ms) = 1h15m30.918s
	// d.Truncate(    1s) = 1h15m30s
	// d.Truncate(    2s) = 1h15m30s
	// d.Truncate(  1m0s) = 1h15m0s
	// d.Truncate( 10m0s) = 1h10m0s
	// d.Truncate(1h0m0s) = 1h0m0s
}

func ExampleParseDuration() {
	hours, _ := time.ParseDuration("10h")
	complex, _ := time.ParseDuration("1h10m10s")
	micro, _ := time.ParseDuration("1µs")
	// The package also accepts the incorrect but common prefix u for micro.
	micro2, _ := time.ParseDuration("1us")

	fmt.Println(hours)
	fmt.Println(complex)
	fmt.Printf("There are %.0f seconds in %v.\n", complex.Seconds(), complex)
	fmt.Printf("There are %d nanoseconds in %v.\n", micro.Nanoseconds(), micro)
	fmt.Printf("There are %6.2e seconds in %v.\n", micro2.Seconds(), micro)
	// Output:
	// 10h0m0s
	// 1h10m10s
	// There are 4210 seconds in 1h10m10s.
	// There are 1000 nanoseconds in 1µs.
	// There are 1.00e-06 seconds in 1µs.
}

func ExampleDuration_Hours() {
	h, _ := time.ParseDuration("4h30m")
	fmt.Printf("I've got %.1f hours of work left.", h.Hours())
	// Output: I've got 4.5 hours of work left.
}

func ExampleDuration_Minutes() {
	m, _ := time.ParseDuration("1h30m")
	fmt.Printf("The movie is %.0f minutes long.", m.Minutes())
	// Output: The movie is 90 minutes long.
}

func ExampleDuration_Nanoseconds() {
	u, _ := time.ParseDuration("1µs")
	fmt.Printf("One microsecond is %d nanoseconds.\n", u.Nanoseconds())
	// Output:
	// One microsecond is 1000 nanoseconds.
}

func ExampleDuration_Seconds() {
	m, _ := time.ParseDuration("1m30s")
	fmt.Printf("Take off in t-%.0f seconds.", m.Seconds())
	// Output: Take off in t-90 seconds.
}

var c chan int

func handle(int) {}

func ExampleAfter() {
	select {
	case m := <-c:
		handle(m)
	case <-time.After(10 * time.Second):
		fmt.Println("timed out")
	}
}

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

func statusUpdate() string { return "" }

func ExampleTick() {
	c := time.Tick(5 * time.Second)
	for now := range c {
		fmt.Printf("%v %s\n", now, statusUpdate())
	}
}

func ExampleMonth() {
	_, month, day := time.Now().Date()
	if month == time.November && day == 10 {
		fmt.Println("Happy Go day!")
	}
}

func ExampleDate() {
	t := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Printf("Go launched at %s\n", t.Local())
	// Output: Go launched at 2009-11-10 15:00:00 -0800 PST
}

func ExampleNewTicker() {
	ticker := time.NewTicker(time.Second)
	defer ticker.Stop()
	done := make(chan bool)
	go func() {
		time.Sleep(10 * time.Second)
		done <- true
	}()
	for {
		select {
		case <-done:
			fmt.Println("Done!")
			return
		case t := <-ticker.C:
			fmt.Println("Current time: ", t)
		}
	}
}

func ExampleTime_Format() {
	// Parse a time value from a string in the standard Unix format.
	t, err := time.Parse(time.UnixDate, "Sat Mar  7 11:06:39 PST 2015")
	if err != nil { // Always check errors even if they should not happen.
		panic(err)
	}

	// time.Time's Stringer method is useful without any format.
	fmt.Println("default format:", t)

	// Predefined constants in the package implement common layouts.
	fmt.Println("Unix format:", t.Format(time.UnixDate))

	// The time zone attached to the time value affects its output.
	fmt.Println("Same, in UTC:", t.UTC().Format(time.UnixDate))

	// The rest of this function demonstrates the properties of the
	// layout string used in the format.

	// The layout string used by the Parse function and Format method
	// shows by example how the reference time should be represented.
	// We stress that one must show how the reference time is formatted,
	// not a time of the user's choosing. Thus each layout string is a
	// representation of the time stamp,
	//	Jan 2 15:04:05 2006 MST
	// An easy way to remember this value is that it holds, when presented
	// in this order, the values (lined up with the elements above):
	//	  1 2  3  4  5    6  -7
	// There are some wrinkles illustrated below.

	// Most uses of Format and Parse use constant layout strings such as
	// the ones defined in this package, but the interface is flexible,
	// as these examples show.

	// Define a helper function to make the examples' output look nice.
	do := func(name, layout, want string) {
		got := t.Format(layout)
		if want != got {
			fmt.Printf("error: for %q got %q; expected %q\n", layout, got, want)
			return
		}
		fmt.Printf("%-15s %q gives %q\n", name, layout, got)
	}

	// Print a header in our output.
	fmt.Printf("\nFormats:\n\n")

	// A simple starter example.
	do("Basic", "Mon Jan 2 15:04:05 MST 2006", "Sat Mar 7 11:06:39 PST 2015")

	// For fixed-width printing of values, such as the date, that may be one or
	// two characters (7 vs. 07), use an _ instead of a space in the layout string.
	// Here we print just the day, which is 2 in our layout string and 7 in our
	// value.
	do("No pad", "<2>", "<7>")

	// An underscore represents a space pad, if the date only has one digit.
	do("Spaces", "<_2>", "< 7>")

	// A "0" indicates zero padding for single-digit values.
	do("Zeros", "<02>", "<07>")

	// If the value is already the right width, padding is not used.
	// For instance, the second (05 in the reference time) in our value is 39,
	// so it doesn't need padding, but the minutes (04, 06) does.
	do("Suppressed pad", "04:05", "06:39")

	// The predefined constant Unix uses an underscore to pad the day.
	// Compare with our simple starter example.
	do("Unix", time.UnixDate, "Sat Mar  7 11:06:39 PST 2015")

	// The hour of the reference time is 15, or 3PM. The layout can express
	// it either way, and since our value is the morning we should see it as
	// an AM time. We show both in one format string. Lower case too.
	do("AM/PM", "3PM==3pm==15h", "11AM==11am==11h")

	// When parsing, if the seconds value is followed by a decimal point
	// and some digits, that is taken as a fraction of a second even if
	// the layout string does not represent the fractional second.
	// Here we add a fractional second to our time value used above.
	t, err = time.Parse(time.UnixDate, "Sat Mar  7 11:06:39.1234 PST 2015")
	if err != nil {
		panic(err)
	}
	// It does not appear in the output if the layout string does not contain
	// a representation of the fractional second.
	do("No fraction", time.UnixDate, "Sat Mar  7 11:06:39 PST 2015")

	// Fractional seconds can be printed by adding a run of 0s or 9s after
	// a decimal point in the seconds value in the layout string.
	// If the layout digits are 0s, the fractional second is of the specified
	// width. Note that the output has a trailing zero.
	do("0s for fraction", "15:04:05.00000", "11:06:39.12340")

	// If the fraction in the layout is 9s, trailing zeros are dropped.
	do("9s for fraction", "15:04:05.99999999", "11:06:39.1234")

	// Output:
	// default format: 2015-03-07 11:06:39 -0800 PST
	// Unix format: Sat Mar  7 11:06:39 PST 2015
	// Same, in UTC: Sat Mar  7 19:06:39 UTC 2015
	//
	// Formats:
	//
	// Basic           "Mon Jan 2 15:04:05 MST 2006" gives "Sat Mar 7 11:06:39 PST 2015"
	// No pad          "<2>" gives "<7>"
	// Spaces          "<_2>" gives "< 7>"
	// Zeros           "<02>" gives "<07>"
	// Suppressed pad  "04:05" gives "06:39"
	// Unix            "Mon Jan _2 15:04:05 MST 2006" gives "Sat Mar  7 11:06:39 PST 2015"
	// AM/PM           "3PM==3pm==15h" gives "11AM==11am==11h"
	// No fraction     "Mon Jan _2 15:04:05 MST 2006" gives "Sat Mar  7 11:06:39 PST 2015"
	// 0s for fraction "15:04:05.00000" gives "11:06:39.12340"
	// 9s for fraction "15:04:05.99999999" gives "11:06:39.1234"

}

func ExampleParse() {
	// See the example for Time.Format for a thorough description of how
	// to define the layout string to parse a time.Time value; Parse and
	// Format use the same model to describe their input and output.

	// longForm shows by example how the reference time would be represented in
	// the desired layout.
	const longForm = "Jan 2, 2006 at 3:04pm (MST)"
	t, _ := time.Parse(longForm, "Feb 3, 2013 at 7:54pm (PST)")
	fmt.Println(t)

	// shortForm is another way the reference time would be represented
	// in the desired layout; it has no time zone present.
	// Note: without explicit zone, returns time in UTC.
	const shortForm = "2006-Jan-02"
	t, _ = time.Parse(shortForm, "2013-Feb-03")
	fmt.Println(t)

	// Some valid layouts are invalid time values, due to format specifiers
	// such as _ for space padding and Z for zone information.
	// For example the RFC3339 layout 2006-01-02T15:04:05Z07:00
	// contains both Z and a time zone offset in order to handle both valid options:
	// 2006-01-02T15:04:05Z
	// 2006-01-02T15:04:05+07:00
	t, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
	fmt.Println(t)
	t, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05+07:00")
	fmt.Println(t)
	_, err := time.Parse(time.RFC3339, time.RFC3339)
	fmt.Println("error", err) // Returns an error as the layout is not a valid time value

	// Output:
	// 2013-02-03 19:54:00 -0800 PST
	// 2013-02-03 00:00:00 +0000 UTC
	// 2006-01-02 15:04:05 +0000 UTC
	// 2006-01-02 15:04:05 +0700 +0700
	// error parsing time "2006-01-02T15:04:05Z07:00": extra text: 07:00
}

func ExampleParseInLocation() {
	loc, _ := time.LoadLocation("Europe/Berlin")

	const longForm = "Jan 2, 2006 at 3:04pm (MST)"
	t, _ := time.ParseInLocation(longForm, "Jul 9, 2012 at 5:02am (CEST)", loc)
	fmt.Println(t)

	// Note: without explicit zone, returns time in given location.
	const shortForm = "2006-Jan-02"
	t, _ = time.ParseInLocation(shortForm, "2012-Jul-09", loc)
	fmt.Println(t)

	// Output:
	// 2012-07-09 05:02:00 +0200 CEST
	// 2012-07-09 00:00:00 +0200 CEST
}

func ExampleTime_Unix() {
	// 1 billion seconds of Unix, three ways.
	fmt.Println(time.Unix(1e9, 0).UTC())     // 1e9 seconds
	fmt.Println(time.Unix(0, 1e18).UTC())    // 1e18 nanoseconds
	fmt.Println(time.Unix(2e9, -1e18).UTC()) // 2e9 seconds - 1e18 nanoseconds

	t := time.Date(2001, time.September, 9, 1, 46, 40, 0, time.UTC)
	fmt.Println(t.Unix())     // seconds since 1970
	fmt.Println(t.UnixNano()) // nanoseconds since 1970

	// Output:
	// 2001-09-09 01:46:40 +0000 UTC
	// 2001-09-09 01:46:40 +0000 UTC
	// 2001-09-09 01:46:40 +0000 UTC
	// 1000000000
	// 1000000000000000000
}

func ExampleTime_Round() {
	t := time.Date(0, 0, 0, 12, 15, 30, 918273645, time.UTC)
	round := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
		time.Hour,
	}

	for _, d := range round {
		fmt.Printf("t.Round(%6s) = %s\n", d, t.Round(d).Format("15:04:05.999999999"))
	}
	// Output:
	// t.Round(   1ns) = 12:15:30.918273645
	// t.Round(   1µs) = 12:15:30.918274
	// t.Round(   1ms) = 12:15:30.918
	// t.Round(    1s) = 12:15:31
	// t.Round(    2s) = 12:15:30
	// t.Round(  1m0s) = 12:16:00
	// t.Round( 10m0s) = 12:20:00
	// t.Round(1h0m0s) = 12:00:00
}

func ExampleTime_Truncate() {
	t, _ := time.Parse("2006 Jan 02 15:04:05", "2012 Dec 07 12:15:30.918273645")
	trunc := []time.Duration{
		time.Nanosecond,
		time.Microsecond,
		time.Millisecond,
		time.Second,
		2 * time.Second,
		time.Minute,
		10 * time.Minute,
	}

	for _, d := range trunc {
		fmt.Printf("t.Truncate(%5s) = %s\n", d, t.Truncate(d).Format("15:04:05.999999999"))
	}
	// To round to the last midnight in the local timezone, create a new Date.
	midnight := time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, time.Local)
	_ = midnight

	// Output:
	// t.Truncate(  1ns) = 12:15:30.918273645
	// t.Truncate(  1µs) = 12:15:30.918273
	// t.Truncate(  1ms) = 12:15:30.918
	// t.Truncate(   1s) = 12:15:30
	// t.Truncate(   2s) = 12:15:30
	// t.Truncate( 1m0s) = 12:15:00
	// t.Truncate(10m0s) = 12:10:00
}

func ExampleLoadLocation() {
	location, err := time.LoadLocation("America/Los_Angeles")
	if err != nil {
		panic(err)
	}

	timeInUTC := time.Date(2018, 8, 30, 12, 0, 0, 0, time.UTC)
	fmt.Println(timeInUTC.In(location))
	// Output: 2018-08-30 05:00:00 -0700 PDT
}

func ExampleLocation() {
	// China doesn't have daylight saving. It uses a fixed 8 hour offset from UTC.
	secondsEastOfUTC := int((8 * time.Hour).Seconds())
	beijing := time.FixedZone("Beijing Time", secondsEastOfUTC)

	// If the system has a timezone database present, it's possible to load a location
	// from that, e.g.:
	//    newYork, err := time.LoadLocation("America/New_York")

	// Creating a time requires a location. Common locations are time.Local and time.UTC.
	timeInUTC := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
	sameTimeInBeijing := time.Date(2009, 1, 1, 20, 0, 0, 0, beijing)

	// Although the UTC clock time is 1200 and the Beijing clock time is 2000, Beijing is
	// 8 hours ahead so the two dates actually represent the same instant.
	timesAreEqual := timeInUTC.Equal(sameTimeInBeijing)
	fmt.Println(timesAreEqual)

	// Output:
	// true
}

func ExampleTime_Add() {
	start := time.Date(2009, 1, 1, 12, 0, 0, 0, time.UTC)
	afterTenSeconds := start.Add(time.Second * 10)
	afterTenMinutes := start.Add(time.Minute * 10)
	afterTenHours := start.Add(time.Hour * 10)
	afterTenDays := start.Add(time.Hour * 24 * 10)

	fmt.Printf("start = %v\n", start)
	fmt.Printf("start.Add(time.Second * 10) = %v\n", afterTenSeconds)
	fmt.Printf("start.Add(time.Minute * 10) = %v\n", afterTenMinutes)
	fmt.Printf("start.Add(time.Hour * 10) = %v\n", afterTenHours)
	fmt.Printf("start.Add(time.Hour * 24 * 10) = %v\n", afterTenDays)

	// Output:
	// start = 2009-01-01 12:00:00 +0000 UTC
	// start.Add(time.Second * 10) = 2009-01-01 12:00:10 +0000 UTC
	// start.Add(time.Minute * 10) = 2009-01-01 12:10:00 +0000 UTC
	// start.Add(time.Hour * 10) = 2009-01-01 22:00:00 +0000 UTC
	// start.Add(time.Hour * 24 * 10) = 2009-01-11 12:00:00 +0000 UTC
}

func ExampleTime_AddDate() {
	start := time.Date(2009, 1, 1, 0, 0, 0, 0, time.UTC)
	oneDayLater := start.AddDate(0, 0, 1)
	oneMonthLater := start.AddDate(0, 1, 0)
	oneYearLater := start.AddDate(1, 0, 0)

	fmt.Printf("oneDayLater: start.AddDate(0, 0, 1) = %v\n", oneDayLater)
	fmt.Printf("oneMonthLater: start.AddDate(0, 1, 0) = %v\n", oneMonthLater)
	fmt.Printf("oneYearLater: start.AddDate(1, 0, 0) = %v\n", oneYearLater)

	// Output:
	// oneDayLater: start.AddDate(0, 0, 1) = 2009-01-02 00:00:00 +0000 UTC
	// oneMonthLater: start.AddDate(0, 1, 0) = 2009-02-01 00:00:00 +0000 UTC
	// oneYearLater: start.AddDate(1, 0, 0) = 2010-01-01 00:00:00 +0000 UTC
}

func ExampleTime_After() {
	year2000 := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	year3000 := time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)

	isYear3000AfterYear2000 := year3000.After(year2000) // True
	isYear2000AfterYear3000 := year2000.After(year3000) // False

	fmt.Printf("year3000.After(year2000) = %v\n", isYear3000AfterYear2000)
	fmt.Printf("year2000.After(year3000) = %v\n", isYear2000AfterYear3000)

	// Output:
	// year3000.After(year2000) = true
	// year2000.After(year3000) = false
}

func ExampleTime_Before() {
	year2000 := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	year3000 := time.Date(3000, 1, 1, 0, 0, 0, 0, time.UTC)

	isYear2000BeforeYear3000 := year2000.Before(year3000) // True
	isYear3000BeforeYear2000 := year3000.Before(year2000) // False

	fmt.Printf("year2000.Before(year3000) = %v\n", isYear2000BeforeYear3000)
	fmt.Printf("year3000.Before(year2000) = %v\n", isYear3000BeforeYear2000)

	// Output:
	// year2000.Before(year3000) = true
	// year3000.Before(year2000) = false
}

func ExampleTime_Date() {
	d := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	year, month, day := d.Date()

	fmt.Printf("year = %v\n", year)
	fmt.Printf("month = %v\n", month)
	fmt.Printf("day = %v\n", day)

	// Output:
	// year = 2000
	// month = February
	// day = 1
}

func ExampleTime_Day() {
	d := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	day := d.Day()

	fmt.Printf("day = %v\n", day)

	// Output:
	// day = 1
}

func ExampleTime_Equal() {
	secondsEastOfUTC := int((8 * time.Hour).Seconds())
	beijing := time.FixedZone("Beijing Time", secondsEastOfUTC)

	// Unlike the equal operator, Equal is aware that d1 and d2 are the
	// same instant but in different time zones.
	d1 := time.Date(2000, 2, 1, 12, 30, 0, 0, time.UTC)
	d2 := time.Date(2000, 2, 1, 20, 30, 0, 0, beijing)

	datesEqualUsingEqualOperator := d1 == d2
	datesEqualUsingFunction := d1.Equal(d2)

	fmt.Printf("datesEqualUsingEqualOperator = %v\n", datesEqualUsingEqualOperator)
	fmt.Printf("datesEqualUsingFunction = %v\n", datesEqualUsingFunction)

	// Output:
	// datesEqualUsingEqualOperator = false
	// datesEqualUsingFunction = true
}

func ExampleTime_String() {
	timeWithNanoseconds := time.Date(2000, 2, 1, 12, 13, 14, 15, time.UTC)
	withNanoseconds := timeWithNanoseconds.String()

	timeWithoutNanoseconds := time.Date(2000, 2, 1, 12, 13, 14, 0, time.UTC)
	withoutNanoseconds := timeWithoutNanoseconds.String()

	fmt.Printf("withNanoseconds = %v\n", string(withNanoseconds))
	fmt.Printf("withoutNanoseconds = %v\n", string(withoutNanoseconds))

	// Output:
	// withNanoseconds = 2000-02-01 12:13:14.000000015 +0000 UTC
	// withoutNanoseconds = 2000-02-01 12:13:14 +0000 UTC
}

func ExampleTime_Sub() {
	start := time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)
	end := time.Date(2000, 1, 1, 12, 0, 0, 0, time.UTC)

	difference := end.Sub(start)
	fmt.Printf("difference = %v\n", difference)

	// Output:
	// difference = 12h0m0s
}

func ExampleTime_AppendFormat() {
	t := time.Date(2017, time.November, 4, 11, 0, 0, 0, time.UTC)
	text := []byte("Time: ")

	text = t.AppendFormat(text, time.Kitchen)
	fmt.Println(string(text))

	// Output:
	// Time: 11:00AM
}

func ExampleFixedZone() {
	loc := time.FixedZone("UTC-8", -8*60*60)
	t := time.Date(2009, time.November, 10, 23, 0, 0, 0, loc)
	fmt.Println("The time is:", t.Format(time.RFC822))
	// Output: The time is: 10 Nov 09 23:00 UTC-8
}