#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

int
main(int argc, char *argv[])
{
    struct tm tm;
    char buf[255];

    memset(&tm, 0, sizeof(struct tm));
    if (argc != 3) {
        fprintf(stderr, "Usage:\n  %s date format", argv[0]);
        exit(1);
    }
    strptime(argv[1], argv[2], &tm);
    mktime(&tm);
    strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", &tm);
    puts(buf);
    return 0;
}