[C]time functions

time_t ltime;
struct tm *today;

_tzset();		// time zone 환경변수 세팅
time(&ltime);		// 1970년 1월 1일 부터경과한 초(Sec) 가져옴
today = localtime(&ltime);	// tm structure type 사용
 
printf("%s\n", ctime(&ltime));

// tm structure
 struct tm {
         int tm_sec;     /* seconds after the minute - [0,59] */
         int tm_min;     /* minutes after the hour - [0,59] */
         int tm_hour;    /* hours since midnight - [0,23] */
         int tm_mday;    /* day of the month - [1,31] */
         int tm_mon;     /* months since January - [0,11] */
         int tm_year;    /* years since 1900 */
         int tm_wday;    /* days since Sunday - [0,6] */
         int tm_yday;    /* days since January 1 - [0,365] */
         int tm_isdst;   /* daylight savings time flag */
         };