checks 'Y-m-d H:s:i' if date is today, tomorrow, already passed or anything else

/**
 * 
 * @param datetime $date_to_check
 * @param datetime $now
 * @return string
 */
function check_date($date_to_check, $now=null) {
  
  // setting now
  if ($now == null) $now = new DateTime();
  
  // get difference
  $date_to_check = new DateTime($date_to_check);
  $interval = $now->diff($date_to_check);
  
  // checking for today
  if ($interval->format('%R%a %H %i') == '+0 0 0') {
    return 'today';
  }
  
  // checking for tomorrow
  if ($interval->format('%R%a %H %i') == '+1 0 0') {
    return 'tomorrow';
  }
  
  // checking for already passed
  if ($interval->format('%R%a %H %i') == '-0 0 0') {
    return 'already passed';
  }