在 Go 中将 UTC 转换为 "local" 时间

Question

如何将UTC时间转换为本地时间?

我已经创建了一个地图，其中包含所有我需要的当地时间的国家的UTC差异。然后，我将该差异作为持续时间添加到当前时间(UTC)，并打印结果，希望这是该特定国家的当地时间。

由于某些原因，结果是错误的。比如匈牙利就有一个小时的时差。知道我为什么会得到错误的结果吗?

package main
import "fmt"
import "time"
func main() {
    m := make(map[string]string)
    m["Hungary"] = "+01.00h"
    offSet, err := time.ParseDuration(m["Hungary"])
    if err != nil {
        panic(err)
    }
    t := time.Now().UTC().Add(offSet)
    nice := t.Format("15:04")
    fmt.Println(nice)
}

Answer 1

请记住，操场的时间设置为2009-11-10 23:00:00 +0000 UTC，所以它是工作的。

正确的方法是使用time.LoadLocation，这里有一个例子:

var countryTz = map[string]string{
    "Hungary": "Europe/Budapest",
    "Egypt":   "Africa/Cairo",
}
func timeIn(name string) time.Time {
    loc, err := time.LoadLocation(countryTz[name])
    if err != nil {
        panic(err)
    }
    return time.Now().In(loc)
}
func main() {
    utc := time.Now().UTC().Format("15:04")
    hun := timeIn("Hungary").Format("15:04")
    eg := timeIn("Egypt").Format("15:04")
    fmt.Println(utc, hun, eg)
}

Answer 2

你的方法有缺陷。一个国家可以有几个时区，例如，美国和俄罗斯。由于实行夏令时，一个时区可以有多个时间，例如匈牙利。匈牙利是UTC+ 1:00，夏令时也是UTC+2:00。

对于您想要给定UTC时间的本地时间的每个位置，使用IANA (tzdata)时区位置。例如,

package main
import (
    "fmt"
    "time"
)
func main() {
    utc := time.Now().UTC()
    fmt.Println(utc)
    local := utc
    location, err := time.LoadLocation("Europe/Budapest")
    if err == nil {
        local = local.In(location)
    }
    fmt.Println("UTC", utc.Format("15:04"), local.Location(), local.Format("15:04"))
    local = utc
    location, err = time.LoadLocation("America/Los_Angeles")
    if err == nil {
        local = local.In(location)
    }
    fmt.Println("UTC", utc.Format("15:04"), local.Location(), local.Format("15:04"))
}

输出:

2014-08-14 23:57:09.151377514 +0000 UTC
UTC 23:57 Europe/Budapest 01:57
UTC 23:57 America/Los_Angeles 16:57

引用:

IANA时区数据库

tz数据库

数据库时区

时区

匈牙利时间

Answer 3

使用location "Local"来节省使用特定区域的麻烦。以下是本地和UTC转换的完整且实用的示例:

package main
import (
    "fmt"
    "log"
    "time"
)
const (
    dateTimeFormat = "2006-01-02 15:04 MST"
    dateFormat    = "2006-01-02"
    timeFormat    = "15:04"
)
// A full cycle example of receiving local date and time,
// handing off to a database, retrieving as UTC, and formatting as local datetime
// This should be good in *any* timezone
func main() {
    // If using a form for entry, I strongly suggest a controlled format input like
    // <input type="date" ... > and <input type="time" ... >
    locallyEnteredDate := "2017-07-16"
    locallyEnteredTime := "14:00"
    // Build a time object from received fields (time objects include zone info)
    // We are assuming the code is running on a server that is in the same zone as the current user
    zone, _ := time.Now().Zone() // get the local zone
    dateTimeZ := locallyEnteredDate + " " + locallyEnteredTime + " " + zone
    dte, err := time.Parse(dateTimeFormat, dateTimeZ)
    if err != nil {
        log.Fatal("Error parsing entered datetime", err)
    }
    fmt.Println("dte:", dte) // dte is a legit time object
    // Perhaps we are saving this in a database.
    // A good database driver should save the time object as UTC in a time with zone field,
    // and return a time object with UTC as zone.
    // For the sake of this example, let's assume an object identical to `dte` is returned
    // dte := ReceiveFromDatabase()
    // Convert received date to local.
    // Note the use of the convenient "Local" location https://golang.org/pkg/time/#LoadLocation.
    localLoc, err := time.LoadLocation("Local")
    if err != nil {
        log.Fatal(`Failed to load location "Local"`)
    }
    localDateTime := dte.In(localLoc)
    fmt.Println("Date:", localDateTime.Format(dateFormat))
    fmt.Println("Time:", localDateTime.Format(timeFormat))
}

Answer 4

注意:最好使用你的编辑器而不是go playground。

package main
import (
    "fmt"
    "time"
)
func main() {
    now := time.Now()
    location, _ := time.LoadLocation("UTC")
    fmt.Printf("UTC time is ------ %sn", now.In(location))
    location, _ = time.LoadLocation("Europe/Berlin")
    fmt.Printf("Berlin time is ------ %sn", now.In(location))
    location, _ = time.LoadLocation("Africa/Casablanca")
    fmt.Printf("Casablanca time is ------ %sn", now.In(location))
    location, _ = time.LoadLocation("Asia/Dubai")
    fmt.Printf("Dubai time is ------ %sn", now.In(location))
}