#include <time.h>
#include <string.h>
#include <stdio.h>

static unsigned print_decimal(size_t places, char buf[places], unsigned val) {
  for (size_t pos = places; pos > 0; pos--) {
    buf[pos-1] = (val % 10) + '0';
    val /= 10;
  }
  return val;
}

char *asctime_r(const struct tm *tm, char *buf) {
  static char const wday[7][3] = {
                                "Sun",
                                "Mon",
                                "Tue",
                                "Wed",
                                "Thu",
                                "Fri",
                                "Sat",
  };
  static char const mon[12][3] = {
                                "Jan",
                                "Feb",
                                "Mar",
                                "Apr",
                                "May",
                                "Jun",
                                "Jul",
                                "Aug",
                                "Sep",
                                "Oct",
                                "Nov",
                                "Dec",
  };
  memcpy(buf, "\0\0\0 \0\0\0  \0 \0\0:\0\0:\0\0 \0\0\0\0\n", 26);

  if (tm->tm_wday >= 7u) goto CLEANUP;
  memcpy(buf, wday[tm->tm_wday], 3);

  if (tm->tm_mon >= 12u) goto CLEANUP;
  memcpy(buf+4, mon[tm->tm_mon], 3);

  if (tm->tm_mday < 10u) {
    if (print_decimal(1, buf+9, tm->tm_mday)) goto CLEANUP;
  } else {
    if (print_decimal(2, buf+8, tm->tm_mday)) goto CLEANUP;
  }
  if (print_decimal(2, buf+11, tm->tm_hour)) goto CLEANUP;
  if (print_decimal(2, buf+14, tm->tm_min)) goto CLEANUP;
  if (print_decimal(2, buf+17, tm->tm_sec)) goto CLEANUP;
  if (1900u+tm->tm_year < 1000u || print_decimal(4, buf+20, 1900u+tm->tm_year)) goto CLEANUP;

 CLEANUP:
  return buf;
}


int main(int argc, char* argv[argc+1]) {
  char buf[26];
  struct tm T;
  time_t t = time(0);
  gmtime_r(&t, &T);
  if (argc == 2) T.tm_mon = 13;
  if (argc == 3) T.tm_mon = -6;
  asctime_r(&T, buf);
  puts(buf);
  //puts(asctime(&T));
}