compare between Dates

Date.compare.js

(function () {
  /**
   * compare date, return 0 = equals, 1 = date1 > date2, -1 = date1 < date2
   * @param {String} date1 string in W3C format (Y-m-d\TH:i:sP)
   * @param {String} date2 string in W3C format (Y-m-d\TH:i:sP)
   * @return {int|bool} false if dates are invalid, 0 = equals, 1 = date1 > date2, -1 = date1 < date2
   */
  Date.compare = function (date1, date2) {
    if (! (date1 instanceof Date)) {
      date1 = new Date(date1);
    }
    if (! (date2 instanceof Date)) {
      date2 = new Date(date2);
    }

    date1 = +date1;
    date2 = +date2;

    if (isNaN(date1) || isNaN(date2)) {
      return false;
    }

    return (date1 > date2)-(date1 < date2);
  }
})();

// with Date
console.log(Date.compare(new Date('2015-02-04'), new Date('2015-02-04'))); // 0
console.log(Date.compare(new Date('2015-02-01'), new Date('2015-02-04'))); // -1
console.log(Date.compare(new Date('2015-02-10'), new Date('2015-02-04'))); // 1
// with String
console.log(Date.compare('2015-02-04T20:50:30', '2015-02-04T20:50:30')); // 0
console.log(Date.compare('2015-02-04T19:50:30', '2015-02-04T21:50:30')); // -1
console.log(Date.compare('2015-02-04T20:50:30', '2015-02-04T19:50:30')); // 1