/* Find all Friday The 13th birthdays for person born Nov 13, 1973 */
#include <time.h>
#include <stdio.h>

int main( void )
{
  const int FRIDAY = 6 - 1;          /* Sunday Is 0, etc... */
  struct tm theTime = { 0 };         /* Set all fields To 0 */
  int year;

  theTime.tm_mon = 11 - 1;           /* January is 0, etc... */
  theTime.tm_mday = 13;              /* 13th day of the month */

  for( year = 1973; year < 2073; year++ )
  {
    theTime.tm_year = year - 1900;   /* 1900 is 0, etc... */
    if( mktime( &theTime ) == -1 )
    {
      printf( "mktime failed in %d\n", year );
      break;
    }
    if( theTime.tm_wday == FRIDAY )
      printf( "%s", asctime( &theTime ) );
  }

  return 0;
}