golang的时区和神奇的time.Parse的使用方法
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' <= 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:
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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