C local time & UTC time

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#include "stdafx.h"

#include <time.h>

//time，asctime，gmtime，localtime, mktime

//在先说明的C语言时间函数

//time_t time(time_t *timer);

//double difftime(time_t time1,time_t time2); //得到时间差

//struct tm *gmtime(const time_t *timer); //把日历时间转换成国际时间

//struct tm *localtime(const time_t *timer);

//char *asctime(const struct tm *timeptr); /将时间和日期以字符串格式表示

//char *ctime(const time_t *timer); //得到字符串表示的时间

//size_t strftime(char *s,size_t maxsize,const char *format,const struct tm *timeptr); //设定指定格式的时间

//time_t mktime(struct tm *timeptr); //设置时间

//clock_t clock(void) //得到处理器时间

int _tmain(int argc, _TCHAR* argv[])

{

time_t t=time(NULL);

printf("time_t: %ld\n", t);

tm *tLocal = localtime(&t);

printf("local time %d-%d-%d-%d-%d-%d tm_wday: %d, tm_yday: %d, tm_isdst: %d\n",

tLocal->tm_year+1900, tLocal->tm_mon+1, tLocal->tm_mday,

tLocal->tm_hour, tLocal->tm_min, tLocal->tm_sec,

tLocal->tm_wday, tLocal->tm_yday, tLocal->tm_isdst);

time_t ttLocal = mktime(tLocal);

printf("mktime(ttLocal): %ld\n", ttLocal);

tm *tUTC = gmtime(&t);

printf("UTC__ time %d-%d-%d-%d-%d-%d tm_wday: %d, tm_yday: %d, tm_isdst: %d\n",

tUTC->tm_year+1900, tUTC->tm_mon+1, tUTC->tm_mday,

tUTC->tm_hour, tUTC->tm_min, tUTC->tm_sec,

tUTC->tm_wday, tUTC->tm_yday, tUTC->tm_isdst);

time_t ttUTC = mktime(tUTC);

printf("mktime(tUTC)___: %ld\n", ttUTC);

return 0;

}

////////////////////////////////////////////////////////////////////////////////////////////

time_t: 1421303547

local time 2015-1-15-14-32-27 tm_wday: 4, tm_yday: 14, tm_isdst: 0

mktime(ttLocal): 1421303547

UTC__ time 2015-1-15-6-32-27 tm_wday: 4, tm_yday: 14, tm_isdst: 0

mktime(tUTC)___: 1421274747

注：1.tm *tLocal的值会被tm *tUTC清除，故取得tUTC值后，不能再使用tLocal值。

2.local time与utc time相差“时区”个小时，使用mktime转化成秒后，依然相差“时区”个小时

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