效率对比：构造100W个时间对象

# Perl(Time::Piece)
$ time perl -MTime::Piece -e 'for(1..1000000){$t = Time::Piece->strptime("2017-03-23 16:30:15", "%Y-%m-%d %H:%M:%S")}'
real    0m13.045s
user    0m11.969s
sys     0m0.011s

# Ruby(Time)
$ time ruby -e '1000000.times {|x| t=Time.new(2017,3,23,16,30,15)}'
real    0m2.755s
user    0m1.781s
sys     0m0.767s

$ time ruby -e '1000000.times {|x| t=Time.new(2017,3,23,16,30,15,"+08:00")}'

real    0m0.685s
user    0m0.500s
sys     0m0.203s

# Ruby(Datetime)
$ time ruby -r'date' -e '1000000.times {|x| t = DateTime.strptime("2017-03-23 16:30:15", "%Y-%m-%d %H:%M:%S")}'
real    0m0.994s
user    0m0.885s
sys     0m0.036s

$ time ruby -r'date' -e '1000000.times {|x| t = DateTime.new(2017,3,23,16,30,15)}'
real    0m0.450s
user    0m0.234s
sys     0m0.219s

# Python
import time

fmt = "%Y-%m-%d %H:%M:%S"
for i in range(0,1000000):
        time.strptime("2017-10-23 12:30:23", fmt)

$ time python3 a.py
real    0m8.411s
user    0m7.805s
sys     0m0.094s

# Golang
package main

import (
        "time"
)

func main() {
        const format = "2006-01-02 15:04:05"
        for i := 1; i < 1000000;i++ {
                time.Parse(format, "2018-03-23 16:30:15")
        }
}

$ time go run a.go       # 编译加执行的go程序

real    0m0.267s
user    0m0.213s
sys     0m0.070s

$ time ./a         # 编译过后的go程序

real    0m0.176s
user    0m0.162s
sys     0m0.001s