code: function(elem, date, onDate, minDate, maxDate) {
  			var dateInfo = (typeof onDate === 'boolean' ? {selectable: onDate} :
  				(!$.isFunction(onDate) ? {} : onDate.apply(elem, [date, true])));
  			return (dateInfo.selectable !== false) &&
  				(!minDate || date.toJD() >= minDate.toJD()) && (!maxDate || date.toJD() <= maxDate.toJD());
  		}
docs: Internally determine whether a date is selectable for this datepicker.
  @memberof CalendarsPicker
  @private
  @param elem {Element} the control to check.
  @param date {CDate} The date to check.
  @param onDate {function|boolean} Any <code>onDate</code> callback or <code>callback.selectable</code>.
  @param minDate {CDate} The minimum allowed date.
  @param maxDate {CDate} The maximum allowed date.
  @return {boolean} <code>true</code> if selectable, <code>false</code> if not.