c shell perl php下的日期时间转换: 秒数与人类可读日期 scalar localtime 与 seconds since `00:00:00 1970-01-01 UTC' scalar localtime 26-byte string 与 seconds since `00:00:00 1970-01-01 UTC' （1970年1月1日凌晨零点以来的秒数） the number of seconds that have passed since the Epoch: 00:00:00 January 1, 1970, Coordinated Universal Time (UTC).
c: 《Advanced Programming in the UNIX Environment: Second Edition》 简称《APUE》 Seciont 6.10 Figure 6.8. Relationship of the various time functions 说的清楚 #include time.h> time_t time(time_t *calptr); struct tm *localtime(const time_t *calptr); struct tm *gmtime(const time_t *calptr); time_t mktime(struct tm *tmptr); char *asctime(const struct tm *tmptr); char *ctime(const time_t *calptr); size_t strftime(char *restrict buf, size_t maxsize, const char *restrict format, const struct tm *restrict tmptr);
shell: % date +%s 1128621784
% date -d "1970-01-01 UTC 1128621784 seconds" Fri Oct 7 02:03:04 CST 2005
date -d "1970-01-01 UTC 1128621784 seconds" +"%Y-%m-%d %H:%M:%S" 2005-10-07 02:03:04
