How to pass date in angulajs GET request

Use the invariant format yyyy-MM-dd. Since you're passing the value in the query-string, it will be parsed using the invariant culture:
Melvyn Harbour - MVC ModelBinder and Localization[^]

If you want to include the time, you could use either Date.prototype.toJSON()[^] or Date.prototype.toISOString()[^].

Otherwise, if you don't have an existing date-formatting function, you can roll your own:

if (!Date.prototype.toISODateString) {
  (function() {

    function pad(number) {
      if (number < 10) {
        return '0' + number;
      }
      return number;
    }

    Date.prototype.toISODateString = function() {
      return this.getUTCFullYear() +
        '-' + pad(this.getUTCMonth() + 1) +
        '-' + pad(this.getUTCDate());
    };
  }());
}

...

var response = $http.get(config.apiUrl + "GetMonthDates/" + writedate.toISODateString() + "?IsTodayDate=" + IsTodayDate);