编程离不开时间，时间管理，严格的说分成两块，一个是当前的时刻，对应的是一个点，还有是一段时间间隔。本文简单的讲讲go的时间相关的编程，比较简单，高手可以一笑而过。
golang对时间的支持，是package time做的事儿，里面有好多的函数，我就不一一举例学习，毕竟这是官方文档干的事情。我们初步的学习下常用的函数。
第一个是UNIX epoch time，确切的说就是自1970-01-01 00：00：00 GMT以来的秒数，不知道如何获取的，可以在shell下执行 date +%s
golang中一个很重要的表征时间的数据类型是Time，基本就是三个成员变量 sec ，nsec，Location，详细意思可以参看注释。
type Time struct {
// sec gives the number of seconds elapsed since
// January 1, year 1 00:00:00 UTC.
sec int64
// nsec specifies a non-negative nanosecond
// offset within the second named by Seconds.
// It must be in the range [0, 999999999].
nsec int32
// loc specifies the Location that should be used to
// determine the minute, hour, month, day, and year
// that correspond to this Time.
// Only the zero Time has a nil Location.
// In that case it is interpreted to mean UTC.
loc *Location
}
OK，如何取到UNIX epoch time.
now := time.Now()
用time package中Now()函数获取到当前的时间信息，Now()函数非常的重要，他是后面一切转换的起始点。从Now()我们获取到了Time，从Time类型我们从容的获取到UNIX epoch time ,自然获取到year ，month ，day，weekday, hour,minute,second,nanosecond.
获取UNIX epoch time：
var epoch_seconds int64 = now.Unix()
获取Year
func (t Time) Year() int cur_year := now.Year()
获取Month
func (t Time) Month() Month
cur_month := now.Month()
if cur_month == time.November {
...
}
Month是int类型，fmt.Printf("%v") 或者fmt.Println可以打印出November来，同时Month type有String()函数，输出“November”这样的字符串
const ( January Month = 1 + iota February March April May June July August September October November December )
year mon day，这些都可以在Date函数中一并返回：
func (t Time) Date() (year int, month Month, day int) year,mon,day = now.Date()
获取Hour
func (t Time) Hour() int cur_hour := now.Hour()
Minute可以通过Minute()返回，second可以通过Second()返回。
time还提供了Clock()的同时返回 hour,minute,second = now.Clock().
package main
import "fmt"
import "time"
func main(){
now := time.Now()
year,mon,day := now.UTC().Date()
hour,min,sec := now.UTC().Clock()
zone,_ := now.UTC().Zone()
fmt.Printf("UTC time is %d-%d-%d %02d:%02d:%02d %s\n",
year,mon,day,hour,min,sec,zone)
year,mon,day = now.Date()
hour,min,sec = now.Clock()
zone,_ = now.Zone()
fmt.Printf("local time is %d-%d-%d %02d:%02d:%02d %s\n",
year,mon,day,hour,min,sec,zone)
}
go版本的输出 --------------------- UTC time is 2013-11-22 15:51:22 UTC local time is 2013-11-22 23:51:22 CST
我们另一个关心的话题，是时间间隔，比如我们profile一个以非常耗时的function，我们会在函数开始前记下时刻值，函数结束后，再次记录下时刻值，然后两者的差值，就是函数运行时间。
这表明Time是可以相减的
start_time := time.Now() expensive_function end_time :=time.Now() var duration Duration = end_time.Sub(start_time)
Duration是一种数据类型，其实是个int64类型，表征的是两个时刻之间的纳秒数。
type Duration int64 const ( Nanosecond Duration = 1 Microsecond = 1000 * Nanosecond Millisecond = 1000 * Microsecond Second = 1000 * Millisecond Minute = 60 * Second Hour = 60 * Minute )
Duration类型有Minutes()/Second()/Nanoseconds(), 将duration折算成分钟/秒/纳秒。
now := time.Now()
time.Sleep(3*time.Second);
end_time := time.Now()
var dur_time time.Duration = end_time.Sub(now)
var elapsed_min float64 = dur_time.Minutes()
var elapsed_sec float64 = dur_time.Seconds()
var elapsed_nano int64 = dur_time.Nanoseconds()
fmt.Printf("elasped %f minutes or \nelapsed %f seconds or \nelapsed %d nanoseconds\n",
elapsed_min,elapsed_sec,elapsed_nano)
输出如下
elasped 0.050005 minutes or elapsed 3.000292 seconds or elapsed 3000292435 nanoseconds
Go中的time.Sleep一律是以纳秒为单位的，当然本质是Duration类型：
sleep 3秒可以写成
time.Sleep(3000000000)
time.Sleep(3*time.Second);
package main
import (
"fmt"
"time"
)
const (
date = "2006-01-02"
shortdate = "06-01-02"
times = "15:04:02"
shorttime = "15:04"
datetime = "2006-01-02 15:04:02"
newdatetime = "2006/01/02 15~04~02"
newtime = "15~04~02"
)
func main() {
thisdate := "2014-03-17 14:55:06"
timeformatdate, _ := time.Parse(datetime, thisdate)
fmt.Println(timeformatdate)
convdate := timeformatdate.Format(date)
convshortdate := timeformatdate.Format(shortdate)
convtime := timeformatdate.Format(times)
convshorttime := timeformatdate.Format(shorttime)
convnewdatetime := timeformatdate.Format(newdatetime)
convnewtime := timeformatdate.Format(newtime)
fmt.Println(convdate)
fmt.Println(convshortdate)
fmt.Println(convtime)
fmt.Println(convshorttime)
fmt.Println(convnewdatetime)
fmt.Println(convnewtime)
}
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