function checkDate(startDate, endDate, num, flag) {

    if(startDate == null || endDate == null) {
      popwin.info(' prompt ',' The date cannot be empty ');
      return false;
    }

    if(startDate == '' || endDate == '') {
      popwin.info(' prompt ',' Please enter the query date ');
      return false;
    }

    var start_date = startDate + " 00:00";
    var end_date = endDate + " 00:00";
    start_date = new Date(start_date.replace(/-/g, "/"));
    end_date = new Date(end_date.replace(/-/g, "/"));
    if(start_date > end_date){
      popwin.info(' prompt ',' The deadline must not be less than the start date ');
      return false;
    }

    //Gets the date after num day
    var currentDate = new Date();
    currentDate.setDate(currentDate.getDate() + num);

    if(end_date > currentDate) {
      popwin.info(' prompt ',' The deadline cannot be greater than ' + num + ' The date after the day ');
      return false;
    }

    //Determine whether to cross - month query
    if(flag == false) {
      if(start_date.getMonth() != end_date.getMonth()) {
        popwin.info(' prompt ',' This query does not support cross-month queries ');
        return false;
      }
    }
  }