当前位置 博文首页 > golang的时区和神奇的time.Parse的使用方法
先写一段测试代码：
const TIME_LAYOUT = "2006-01-02 15:04:05"
func parseWithLocation(name string, timeStr string) (time.Time, error) {
locationName := name
if l, err := time.LoadLocation(locationName); err != nil {
println(err.Error())
return time.Time{}, err
} else {
lt, _ := time.ParseInLocation(TIME_LAYOUT, timeStr, l)
fmt.Println(locationName, lt)
return lt, nil
}
}
func testTime() {
fmt.Println("0. now: ", time.Now())
str := "2018-09-10 00:00:00"
fmt.Println("1. str: ", str)
t, _ := time.Parse(TIME_LAYOUT, str)
fmt.Println("2. Parse time: ", t)
tStr := t.Format(TIME_LAYOUT)
fmt.Println("3. Format time str: ", tStr)
name, offset := t.Zone()
name2, offset2 := t.Local().Zone()
fmt.Printf("4. Zone name: %v, Zone offset: %v\n", name, offset)
fmt.Printf("5. Local Zone name: %v, Local Zone offset: %v\n", name2, offset2)
tLocal := t.Local()
tUTC := t.UTC()
fmt.Printf("6. t: %v, Local: %v, UTC: %v\n", t, tLocal, tUTC)
fmt.Printf("7. t: %v, Local: %v, UTC: %v\n", t.Format(TIME_LAYOUT), tLocal.Format(TIME_LAYOUT), tUTC.Format(TIME_LAYOUT))
fmt.Printf("8. Local.Unix: %v, UTC.Unix: %v\n", tLocal.Unix(), tUTC.Unix())
str2 := "1969-12-31 23:59:59"
t2, _ := time.Parse(TIME_LAYOUT, str2)
fmt.Printf("9. str2：%v，time: %v, Unix: %v\n", str2, t2, t2.Unix())
fmt.Printf("10. %v, %v\n", tLocal.Format(time.ANSIC), tUTC.Format(time.ANSIC))
fmt.Printf("11. %v, %v\n", tLocal.Format(time.RFC822), tUTC.Format(time.RFC822))
fmt.Printf("12. %v, %v\n", tLocal.Format(time.RFC822Z), tUTC.Format(time.RFC822Z))
//指定时区
parseWithLocation("America/Cordoba", str)
parseWithLocation("Asia/Shanghai", str)
parseWithLocation("Asia/Beijing", str)
}
testTime()
输出：
0. now: 2018-09-19 19:06:07.3642781 +0800 CST m=+0.005995601
1. str: 2018-09-10 00:00:00
2. Parse time: 2018-09-10 00:00:00 +0000 UTC
3. Format time str: 2018-09-10 00:00:00
4. Zone name: UTC, Zone offset: 0
5. Local Zone name: CST, Local Zone offset: 28800
6. t: 2018-09-10 00:00:00 +0000 UTC, Local: 2018-09-10 08:00:00 +0800 CST, UTC: 2018-09-10 00:00:00 +0000 UTC
7. t: 2018-09-10 00:00:00, Local: 2018-09-10 08:00:00, UTC: 2018-09-10 00:00:00
8. Local.Unix: 1536537600, UTC.Unix: 1536537600
9. str2：1969-12-31 23:59:59，time: 1969-12-31 23:59:59 +0000 UTC, Unix: -1
10. Mon Sep 10 08:00:00 2018, Mon Sep 10 00:00:00 2018
11. 10 Sep 18 08:00 CST, 10 Sep 18 00:00 UTC
12. 10 Sep 18 08:00 +0800, 10 Sep 18 00:00 +0000
America/Cordoba 2018-09-10 00:00:00 -0300 -03
Asia/Shanghai 2018-09-10 00:00:00 +0800 CST
cannot find Asia/Beijing in zip file C:\Go\/lib/time/zoneinfo.zip
从以上代码的测试结果可以得出几点：
一开始使用time.Parse时很不习惯，因为非常奇怪的layout参数。
除了golang自带定义的layout：
const ( ANSIC = "Mon Jan _2 15:04:05 2006" UnixDate = "Mon Jan _2 15:04:05 MST 2006" RubyDate = "Mon Jan 02 15:04:05 -0700 2006" RFC822 = "02 Jan 06 15:04 MST" RFC822Z = "02 Jan 06 15:04 -0700" // RFC822 with numeric zone RFC850 = "Monday, 02-Jan-06 15:04:05 MST" RFC1123 = "Mon, 02 Jan 2006 15:04:05 MST" RFC1123Z = "Mon, 02 Jan 2006 15:04:05 -0700" // RFC1123 with numeric zone RFC3339 = "2006-01-02T15:04:05Z07:00" RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00" Kitchen = "3:04PM" // Handy time stamps. Stamp = "Jan _2 15:04:05" StampMilli = "Jan _2 15:04:05.000" StampMicro = "Jan _2 15:04:05.000000" StampNano = "Jan _2 15:04:05.000000000" )
还可以自定义layout，比如：
"2006-01-02 15:04:05"
网上基本上都在传说这个日子是golang项目开始创建的时间，为了纪念生日才这样设计，其实这真是无稽之谈瞎扯淡。
网上文章没有找到说的比较清楚的，幸好有源码，打开time.Parse的源码看了一下，发现这个设计很好很科学。
解析layout的主要代码在nextStdChunk方法中：
// nextStdChunk finds the first occurrence of a std string in
// layout and returns the text before, the std string, and the text after.
func nextStdChunk(layout string) (prefix string, std int, suffix string) {
for i := 0; i < len(layout); i++ {
switch c := int(layout[i]); c {
case 'J': // January, Jan
if len(layout) >= i+3 && layout[i:i+3] == "Jan" {
if len(layout) >= i+7 && layout[i:i+7] == "January" {
return layout[0:i], stdLongMonth, layout[i+7:]
}
if !startsWithLowerCase(layout[i+3:]) {
return layout[0:i], stdMonth, layout[i+3:]
}
}
case 'M': // Monday, Mon, MST
if len(layout) >= i+3 {
if layout[i:i+3] == "Mon" {
if len(layout) >= i+6 && layout[i:i+6] == "Monday" {
return layout[0:i], stdLongWeekDay, layout[i+6:]
}
if !startsWithLowerCase(layout[i+3:]) {
return layout[0:i], stdWeekDay, layout[i+3:]
}
}
if layout[i:i+3] == "MST" {
return layout[0:i], stdTZ, layout[i+3:]
}
}
case '0': // 01, 02, 03, 04, 05, 06
if len(layout) >= i+2 && '1' <= layout[i+1] && layout[i+1] <= '6' {
return layout[0:i], std0x[layout[i+1]-'1'], layout[i+2:]
}
case '1': // 15, 1
if len(layout) >= i+2 && layout[i+1] == '5' {
return layout[0:i], stdHour, layout[i+2:]
}
return layout[0:i], stdNumMonth, layout[i+1:]
case '2': // 2006, 2
if len(layout) >= i+4 && layout[i:i+4] == "2006" {
return layout[0:i], stdLongYear, layout[i+4:]
}
return layout[0:i], stdDay, layout[i+1:]
case '_': // _2, _2006
if len(layout) >= i+2 && layout[i+1] == '2' {
//_2006 is really a literal _, followed by stdLongYear
if len(layout) >= i+5 && layout[i+1:i+5] == "2006" {
return layout[0 : i+1], stdLongYear, layout[i+5:]
}
return layout[0:i], stdUnderDay, layout[i+2:]
}
case '3':
return layout[0:i], stdHour12, layout[i+1:]
case '4':
return layout[0:i], stdMinute, layout[i+1:]
case '5':
return layout[0:i], stdSecond, layout[i+1:]
case 'P': // PM
if len(layout) >= i+2 && layout[i+1] == 'M' {
return layout[0:i], stdPM, layout[i+2:]
}
case 'p': // pm
if len(layout) >= i+2 && layout[i+1] == 'm' {
return layout[0:i], stdpm, layout[i+2:]
}
case '-': // -070000, -07:00:00, -0700, -07:00, -07
if len(layout) >= i+7 && layout[i:i+7] == "-070000" {
return layout[0:i], stdNumSecondsTz, layout[i+7:]
}
if len(layout) >= i+9 && layout[i:i+9] == "-07:00:00" {
return layout[0:i], stdNumColonSecondsTZ, layout[i+9:]
}
if len(layout) >= i+5 && layout[i:i+5] == "-0700" {
return layout[0:i], stdNumTZ, layout[i+5:]
}
if len(layout) >= i+6 && layout[i:i+6] == "-07:00" {
return layout[0:i], stdNumColonTZ, layout[i+6:]
}
if len(layout) >= i+3 && layout[i:i+3] == "-07" {
return layout[0:i], stdNumShortTZ, layout[i+3:]
}
case 'Z': // Z070000, Z07:00:00, Z0700, Z07:00,
if len(layout) >= i+7 && layout[i:i+7] == "Z070000" {
return layout[0:i], stdISO8601SecondsTZ, layout[i+7:]
}
if len(layout) >= i+9 && layout[i:i+9] == "Z07:00:00" {
return layout[0:i], stdISO8601ColonSecondsTZ, layout[i+9:]
}
if len(layout) >= i+5 && layout[i:i+5] == "Z0700" {
return layout[0:i], stdISO8601TZ, layout[i+5:]
}
if len(layout) >= i+6 && layout[i:i+6] == "Z07:00" {
return layout[0:i], stdISO8601ColonTZ, layout[i+6:]
}
if len(layout) >= i+3 && layout[i:i+3] == "Z07" {
return layout[0:i], stdISO8601ShortTZ, layout[i+3:]
}
case '.': // .000 or .999 - repeated digits for fractional seconds.
if i+1 < len(layout) && (layout[i+1] == '0' || layout[i+1] == '9') {
ch := layout[i+1]
j := i + 1
for j < len(layout) && layout[j] == ch {
j++
}
// String of digits must end here - only fractional second is all digits.
if !isDigit(layout, j) {
std := stdFracSecond0
if layout[i+1] == '9' {
std = stdFracSecond9
}
std |= (j - (i + 1)) << stdArgShift
return layout[0:i], std, layout[j:]
}
}
}
}
return layout, 0, ""
}
可以发现layout的所有代表年月日时分秒甚至时区的值都是互斥不相等的。
比如年份：短年份06，长年份2006，
月份：01，Jan，January
日：02，2，_2
时：15，3，03
分：04， 4
秒：05， 5
因为都不相等所以通过遍历layout就可以switch case解析出每个区块的意义和在字符串中的位置，这样输入对应格式的时间字符串就可以顺利解析出来。
这样layout也可以自定义，而且顺序任意，只要符合下列每个区块定义的规则即可，
代码中的注释就是规则写法：
const ( _ = iota stdLongMonth = iota + stdNeedDate // "January" stdMonth // "Jan" stdNumMonth // "1" stdZeroMonth // "01" stdLongWeekDay // "Monday" stdWeekDay // "Mon" stdDay // "2" stdUnderDay // "_2" stdZeroDay // "02" stdHour = iota + stdNeedClock // "15" stdHour12 // "3" stdZeroHour12 // "03" stdMinute // "4" stdZeroMinute // "04" stdSecond // "5" stdZeroSecond // "05" stdLongYear = iota + stdNeedDate // "2006" stdYear // "06" stdPM = iota + stdNeedClock // "PM" stdpm // "pm" stdTZ = iota // "MST" stdISO8601TZ // "Z0700" // prints Z for UTC stdISO8601SecondsTZ // "Z070000" stdISO8601ShortTZ // "Z07" stdISO8601ColonTZ // "Z07:00" // prints Z for UTC stdISO8601ColonSecondsTZ // "Z07:00:00" stdNumTZ // "-0700" // always numeric stdNumSecondsTz // "-070000" stdNumShortTZ // "-07" // always numeric stdNumColonTZ // "-07:00" // always numeric stdNumColonSecondsTZ // "-07:00:00" stdFracSecond0 // ".0", ".00", ... , trailing zeros included stdFracSecond9 // ".9", ".99", ..., trailing zeros omitted stdNeedDate = 1 << 8 // need month, day, year stdNeedClock = 2 << 8 // need hour, minute, second stdArgShift = 16 // extra argument in high bits, above low stdArgShift stdMask = 1<<stdArgShift - 1 // mask out argument )
时区使用：MST
时区偏移使用-0700或者Z0700等等。
下面是一个使用时区的例子，Z0700比较特殊，当输入时间直接使用Z时就直接代表UTC时区。
func testTimeParse() {
t, _ := time.Parse("2006-01-02 15:04:05 -0700 MST", "2018-09-20 15:39:06 +0800 CST")
fmt.Println(t)
t, _ = time.Parse("2006-01-02 15:04:05 -0700 MST", "2018-09-20 15:39:06 +0000 CST")
fmt.Println(t)
t, _ = time.Parse("2006-01-02 15:04:05 Z0700 MST", "2018-09-20 15:39:06 +0800 CST")
fmt.Println(t)
t, _ = time.Parse("2006-01-02 15:04:05 Z0700 MST", "2018-09-20 15:39:06 Z GMT")
fmt.Println(t)
t, _ = time.Parse("2006-01-02 15:04:05 Z0700 MST", "2018-09-20 15:39:06 +0000 GMT")
fmt.Println(t)
}
输出：
2018-09-20 15:39:06 +0800 CST
2018-09-20 15:39:06 +0000 CST
2018-09-20 15:39:06 +0800 CST
2018-09-20 15:39:06 +0000 UTC
2018-09-20 15:39:06 +0000 GMT
还有疑问的可以看看go自带的测试例子：Go/src/time/example_test.go
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