#include <time.h>

time_t time(time_t *t);

#include <time.h>
main(){
  int seconds = time((time_t*)NULL);
  printf("%d\n", seconds);
}

9.73E+08

#include <time.h>

struct tm *gmtime(const time_t *timep);

struct tm{
  int tm_sec; //代表目前秒数, 正常范围为0-59, 但允许至61 秒
  int tm_min; //代表目前分数, 范围0-59
  int tm_hour; //从午夜算起的时数, 范围为0-23
  int tm_mday; //目前月份的日数, 范围01-31
  int tm_mon; //代表目前月份, 从一月算起, 范围从0-11
  int tm_year; //从1900 年算起至今的年数
  int tm_wday; //一星期的日数, 从星期一算起, 范围为0-6
  int tm_yday; //从今年1 月1 日算起至今的天数, 范围为0-365
  int tm_isdst; //日光节约时间的旗标
};

#include <time.h>
main(){
  char *wday[] = {"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"};
  time_t timep;
  struct tm *p;
  time(&timep);
  p = gmtime(&timep);
  printf("%d%d%d", (1900+p->tm_year), (1+p->tm_mon), p->tm_mday);
  printf("%s%d;%d;%d\n", wday[p->tm_wday], p->tm_hour, p->tm_min, p->tm_sec);
}

2000/10/28 Sat 8:15:38