time

func ParseDuration ¶

func ParseDuration(s string) (Duration, error)

ParseDuration parses a duration string. A duration string is a possibly signed sequence of decimal numbers, each with optional fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".

package main

import (
	"fmt"
	"time"
)

func main() {
	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(), micro2)
}

Output:
10h0m0s
1h10m10s
There are 4210 seconds in 1h10m10s.
There are 1000 nanoseconds in 1µs.
There are 1.00e-06 seconds in 1µs.

func Since ¶

func Since(t Time) Duration

Since returns the time elapsed since t. It is shorthand for time.Now().Sub(t).

package main

import (
	"fmt"
	"time"
)

func expensiveCall() {}

func main() {
	start := time.Now()
	expensiveCall()
	elapsed := time.Since(start)
	fmt.Printf("The call took %v to run.\n", elapsed)
}

Output:

func Until ¶ added in go1.8

func Until(t Time) Duration

Until returns the duration until t. It is shorthand for t.Sub(time.Now()).

package main

import (
	"fmt"
	"math"
	"time"
)

func main() {
	futureTime := time.Now().Add(5 * time.Second)
	durationUntil := time.Until(futureTime)
	fmt.Printf("Duration until future time: %.0f seconds", math.Ceil(durationUntil.Seconds()))
}

Output:
Duration until future time: 5 seconds

func FixedZone ¶

func FixedZone(name string, offset int) *Location

FixedZone returns a Location that always uses the given zone name and offset (seconds east of UTC).

package main

import (
	"fmt"
	"time"
)

func main() {
	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

func LoadLocation ¶

func LoadLocation(name string) (*Location, error)

LoadLocation returns the Location with the given name.

If the name is "" or "UTC", LoadLocation returns UTC. If the name is "Local", LoadLocation returns Local.

Otherwise, the name is taken to be a location name corresponding to a file in the IANA Time Zone database, such as "America/New_York".

LoadLocation looks for the IANA Time Zone database in the following locations in order:

• the directory or uncompressed zip file named by the ZONEINFO environment variable
• on a Unix system, the system standard installation location
• $GOROOT/lib/time/zoneinfo.zip
• the time/tzdata package, if it was imported

package main

import (
	"fmt"
	"time"
)

func main() {
	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 LoadLocationFromTZData ¶ added in go1.10

func LoadLocationFromTZData(name string, data []byte) (*Location, error)

LoadLocationFromTZData returns a Location with the given name initialized from the IANA Time Zone database-formatted data. The data should be in the format of a standard IANA time zone file (for example, the content of /etc/localtime on Unix systems).

func NewTicker ¶

func NewTicker(d Duration) *Ticker

NewTicker returns a new Ticker containing a channel that will send the current time on the channel after each tick. The period of the ticks is specified by the duration argument. The ticker will adjust the time interval or drop ticks to make up for slow receivers. The duration d must be greater than zero; if not, NewTicker will panic.

Before Go 1.23, the garbage collector did not recover tickers that had not yet expired or been stopped, so code often immediately deferred t.Stop after calling NewTicker, to make the ticker recoverable when it was no longer needed. As of Go 1.23, the garbage collector can recover unreferenced tickers, even if they haven't been stopped. The Stop method is no longer necessary to help the garbage collector. (Code may of course still want to call Stop to stop the ticker for other reasons.)

package main

import (
	"fmt"
	"time"
)

func main() {
	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)
		}
	}
}

Output:

func Date ¶

func Date(year int, month Month, day, hour, min, sec, nsec int, loc *Location) Time

Date returns the Time corresponding to

yyyy-mm-dd hh:mm:ss + nsec nanoseconds

in the appropriate zone for that time in the given location.

The month, day, hour, min, sec, and nsec values may be outside their usual ranges and will be normalized during the conversion. For example, October 32 converts to November 1.

A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which.

Date panics if loc is nil.

package main

import (
	"fmt"
	"time"
)

func main() {
	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 Now ¶

func Now() Time

Now returns the current local time.

func Parse ¶

func Parse(layout, value string) (Time, error)

Parse parses a formatted string and returns the time value it represents. See the documentation for the constant called Layout to see how to represent the format. The second argument must be parseable using the format string (layout) provided as the first argument.

The example for Time.Format demonstrates the working of the layout string in detail and is a good reference.

When parsing (only), the input may contain a fractional second field immediately after the seconds field, even if the layout does not signify its presence. In that case either a comma or a decimal point followed by a maximal series of digits is parsed as a fractional second. Fractional seconds are truncated to nanosecond precision.

Elements omitted from the layout are assumed to be zero or, when zero is impossible, one, so parsing "3:04pm" returns the time corresponding to Jan 1, year 0, 15:04:00 UTC (note that because the year is 0, this time is before the zero Time). Years must be in the range 0000..9999. The day of the week is checked for syntax but it is otherwise ignored.

For layouts specifying the two-digit year 06, a value NN >= 69 will be treated as 19NN and a value NN < 69 will be treated as 20NN.

The remainder of this comment describes the handling of time zones.

In the absence of a time zone indicator, Parse returns a time in UTC.

When parsing a time with a zone offset like -0700, if the offset corresponds to a time zone used by the current location (Local), then Parse uses that location and zone in the returned time. Otherwise it records the time as being in a fabricated location with time fixed at the given zone offset.

When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used. The zone abbreviation "UTC" is recognized as UTC regardless of location. If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset. This choice means that such a time can be parsed and reformatted with the same layout losslessly, but the exact instant used in the representation will differ by the actual zone offset. To avoid such problems, prefer time layouts that use a numeric zone offset, or use ParseInLocation.

package main

import (
	"fmt"
	"time"
)

func main() {
	// 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 ParseInLocation ¶ added in go1.1

func ParseInLocation(layout, value string, loc *Location) (Time, error)

ParseInLocation is like Parse but differs in two important ways. First, in the absence of time zone information, Parse interprets a time as UTC; ParseInLocation interprets the time as in the given location. Second, when given a zone offset or abbreviation, Parse tries to match it against the Local location; ParseInLocation uses the given location.

package main

import (
	"fmt"
	"time"
)

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

	// This will look for the name CEST in the Europe/Berlin time zone.
	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 Unix ¶

func Unix(sec int64, nsec int64) Time

Unix returns the local Time corresponding to the given Unix time, sec seconds and nsec nanoseconds since January 1, 1970 UTC. It is valid to pass nsec outside the range [0, 999999999]. Not all sec values have a corresponding time value. One such value is 1<<63-1 (the largest int64 value).

package main

import (
	"fmt"
	"time"
)

func main() {
	unixTime := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(unixTime.Unix())
	t := time.Unix(unixTime.Unix(), 0).UTC()
	fmt.Println(t)

}

Output:
1257894000
2009-11-10 23:00:00 +0000 UTC

func UnixMicro ¶ added in go1.17

func UnixMicro(usec int64) Time

UnixMicro returns the local Time corresponding to the given Unix time, usec microseconds since January 1, 1970 UTC.

package main

import (
	"fmt"
	"time"
)

func main() {
	umt := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(umt.UnixMicro())
	t := time.UnixMicro(umt.UnixMicro()).UTC()
	fmt.Println(t)

}

Output:
1257894000000000
2009-11-10 23:00:00 +0000 UTC

func UnixMilli ¶ added in go1.17

func UnixMilli(msec int64) Time

UnixMilli returns the local Time corresponding to the given Unix time, msec milliseconds since January 1, 1970 UTC.

package main

import (
	"fmt"
	"time"
)

func main() {
	umt := time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
	fmt.Println(umt.UnixMilli())
	t := time.UnixMilli(umt.UnixMilli()).UTC()
	fmt.Println(t)

}

Output:
1257894000000
2009-11-10 23:00:00 +0000 UTC