function check_date(field){
	var checkstr = "0123456789";
	var DateValue = field;
	var Datevalue = "";
	var DateTemp = "";
	var seperator = ".";
	var day;
	var month;
	var year;
	var leap = 0;
	var err = 0;
	var i;
	   err = 0;
	   /* Delete all chars except 0..9 */
	   for (i = 0; i < DateValue.length; i++) {
		  if (checkstr.indexOf(DateValue.substr(i,1)) >= 0) {
		     DateTemp = DateTemp + DateValue.substr(i,1);
		  }
	   }
	   
	   DateValue = DateTemp;
	   /* Always change date to 8 digits - string*/
	   
	   /* if year is entered as 2-digit / always assume 20xx */
	   if (DateValue.length == 6) {
	      DateValue = DateValue.substr(0,4) + '20' + DateValue.substr(4,2); }
	      
	   if (DateValue.length != 8) {
	      err = 19;}
	      
	   /* year is wrong if year = 0000 */
	   year = DateValue.substr(4,4);
	   if (year == 0) {
	      err = 20;
	   }
	   /* Validation of month*/
	   month = DateValue.substr(2,2);
	   if ((month < 1) || (month > 12)) {
	      err = 21;
	   }
	   
	   /* Validation of day*/
	   day = DateValue.substr(0,2);
	   
	   if (day < 1) {
	     err = 22;
	   }
	   /* Validation leap-year / february / day */
	   if ((year % 4 == 0) || (year % 100 == 0) || (year % 400 == 0)) {
	      leap = 1;
	   }
	   if ((month == 2) && (leap == 1) && (day > 29)) {
	      err = 23;
	   }
	   if ((month == 2) && (leap != 1) && (day > 28)) {
	      err = 24;
	   }
	   /* Validation of other months */
	   if ((day > 31) && ((month == "01") || (month == "03") || (month == "05") || (month == "07") || (month == "08") || (month == "10") || (month == "12"))) {
	      err = 25;
	   }
	   if ((day > 30) && ((month == "04") || (month == "06") || (month == "09") || (month == "11"))) {
	      err = 26;
	   }
	   /* if 00 ist entered, no error, deleting the entry */
	   if ((day == 0) && (month == 0) && (year == 00)) {
	      err = 0; day = ""; month = ""; year = ""; seperator = "";
	   }
	   
	   return err;
}