The best string format for string parsing is the date ISO format together with the JavaScript Date object constructor.

Examples of ISO format: YYYY-MM-DD or YYYY-MM-DDTHH:MM:SS.

But wait! Just using the "ISO format" doesn't work reliably by itself. String are sometimes parsed as UTC and sometimes as localtime (based on browser vendor and version). The best practice should always be to store dates as UTC and make computations as UTC.

To parse a date as UTC, append a Z - e.g.: new Date('2011-04-11T10:20:30Z').

To display a date in UTC, use .toUTCString(),
to display a date in user's local time, use .toString().

More info on MDN | Date and this answer.

For old Internet Explorer compatibility (IE versions less than 9 do not support ISO format in Date constructor), you should split datetime string representation to it's parts and then you can use constructor using datetime parts, e.g.: new Date('2011', '04' - 1, '11', '11', '51', '00'). Note that the number of the month must be 1 less.

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Alternate method - use an appropriate library:

You can also take advantage of the library Moment.js that allows parsing date with the specified time zone.

You can check out the JavaScript Date object. You can create a Date object multiple ways, including passing in the exact string in your question: new Date('1977-04-22');. From there, the Date object has a few built in formatting functions like date.toDateString() which outputs Fri Apr 22 1977. (Be careful though. At the moment, for me it outputs 'Thu Apr 21 1977' since creating the date object with a string defaults to UTC time but the output is in my local timezone). https://css-tricks.com/everything-you-need-to-know-about-date-in-javascript/ and other Google results give more details about how to use the Date object.

You need to change that string into a date before you evaluate it in the loop. What is the format of the current string? Inside your for loop do something like this.Option 1 - using vanilla JS (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/parse)const myDate = Date.parse(new Date(result.@mailDate));//thenIf(myDate > date2){} Option 2 - using ACC Date functionconst myDate = formatDate(result.@mailDate, "%4Y/%2M/%2D")//thenIf(myDate > date2){}https://experienceleague.adobe.com/developer/campaign-api/api/f-formatDate.html  Option 3 - using moment JS (be aware library still works although it is not being investing in anymore, but it still makes it easier). This helped me when I was doing advanced date manipulation 100+ lines of JS.https://blog.floriancourgey.com/2018/10/use-javascript-libraries-in-adobe-campaign/  I've done all 3. Which ever fits your context the best is the right one to use.

Altered piece of code I often use:

Date.prototype.yyyymmdd = function() {
  var mm = this.getMonth() + 1; // getMonth() is zero-based
  var dd = this.getDate();

  return [this.getFullYear(),
          (mm>9 ? '' : '0') + mm,
          (dd>9 ? '' : '0') + dd
         ].join('');
};

var date = new Date();
date.yyyymmdd();