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

static void
printtime (long long int t, struct tm tm)
{
  char buf[1000];
  static int n;
  strftime (buf, sizeof buf, "%Y-%m-%d %H:%M:%S %z (%Z)", &tm);
  printf ("%d. %10lld = %s %s\n", ++n, t, buf,
          tm.tm_isdst < 0 ? "unknown" : tm.tm_isdst ? "daylight" : "standard");
}

int
main (void)
{
  setenv ("TZ", "Asia/Tehran", 1);
  time_t t[4] = { 283981500, 283983300, 1640982600, 1656617400 };
  struct tm tm[4];
  int i;
  for (i = 0; i < 4; i++)
    {
      tm[i] = *localtime (&t[i]);
      printtime (t[i], tm[i]);
    }
  for (i = 0; i < 4; i++)
    tm[i] = *localtime (&t[i]);
  for (i = 0; i < 4; i++)
    printtime (t[i], tm[i]);
  return 0;
}