code: function(event) {
  		var inst = $.datepicker._getInst(event.target);
  		if ($.datepicker._get(inst, 'constrainInput')) {
  			var chars = $.datepicker._possibleChars($.datepicker._get(inst, 'dateFormat'));
  			var chr = String.fromCharCode(event.charCode == undefined ? event.keyCode : event.charCode);
  			return event.ctrlKey || event.metaKey || (chr < ' ' || !chars || chars.indexOf(chr) > -1);
  		}
  	}
docs: /* Filter entered characters - based on date format.