/**
  * Returns the earliest known event start date, which can be expected to be a string
  * in MySQL datetime format (unless some other specific format is provided).
  *
  * If this is impossible to determine it will return boolean false.
  *
  * @param string $format
  *
  * @return mixed bool|string
  */
 function tribe_events_earliest_date($format = TribeDateUtils::DBDATETIMEFORMAT)
 {
     // Check if the earliest start date is already known
     $earliest = tribe_get_option('earliest_date', false);
     if (false !== $earliest) {
         return TribeDateUtils::reformat($earliest, $format);
     }
     // If not, try to determine now
     TribeEvents::instance()->rebuild_known_range();
     $earliest = tribe_get_option('earliest_date', false);
     if (false !== $earliest) {
         return TribeDateUtils::reformat($earliest, $format);
     }
     return false;
 }