golang的时区和神奇的time.Parse的使用方法

目录时区神奇的time.Parse 时区：时区

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：

time.Now 得到的当前时间的时区跟电脑的当前时区一样。 time.Parse 把时间字符串转换为Time，时区是UTC时区。不管Time变量存储的是什么时区，其Unix()方法返回的都是距离UTC时间：1970年1月1日0点0分0秒的秒数。 Unix()返回的秒数可以是负数，如果时间小于1970-01-01 00:00:00的话。 Zone方法可以获得变量的时区和时区与UTC的偏移秒数，应该支持夏令时和冬令时。 time.LoadLocation可以根据时区名创建时区Location，所有的时区名字可以在$GOROOT/lib/time/zoneinfo.zip文件中找到，解压zoneinfo.zip可以得到一堆目录和文件，我们只需要目录和文件的名字，时区名是目录名+文件名，比如"Asia/Shanghai"。中国时区名只有"Asia/Shanghai"和"Asia/Chongqing"，而没有"Asia/Beijing"。 time.ParseInLocation可以根据时间字符串和指定时区转换Time。感谢中国只有一个时区而且没有夏令时和冬令时，可怕的美国居然有6个时区，想想都可怕。神奇的time.Parse

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' = 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))