Function isValidDate

codebase/sources/dhtmlxscheduler.es.js:15802–15804

(value)

  return value instanceof Date;
};
var isValidDate = function(value) {
  return isDate(value) && !isNaN(value.getTime());
};
var daysBetween = function(date1, date2) {
  var date1ms = date1.getTime();
  var date2ms = date2.getTime();