INVALID_DATA Error While Setting Date Field in Client Script of Details Page

INVALID_DATA Error While Setting Date Field in Client Script of Details Page

I am trying to detect the Stage change on Details(Standard) page (with the stepper section), then update Stage_Updated_At (Date) field with today's date. 

Thanks to @Anonymous User 's direction, I found this topic and I managed the first part of detecting the change event with onBeforeUpdate.

Here is my code:

var oldValue = ZDK.Page.getField("Stage").getValue();

console.log("Old value : ", oldValue);

console.log("Current value : ", value);

if (oldValue !== value) {

    var record = ZDK.Apps.CRM.Deals.fetchById($Page.record_id);

    var today = new Date();

    var todayLocale = today.toLocaleString('en-us', { month: 'short', day: "numeric", year: 'numeric' });

    record.Stage_Updated_At = todayLocale;

    var response = record.__update();

    ZDK.Client.navigateTo('record_detail', { module: 'Deals', record_id: $Page.record_id });

}

The problem is that I get the following error when I try setting a date object into Stage_Updated_At field.

Uncaught (in promise) ZDKError: {"data":[{"code":"INVALID_DATA","details":{"expected_data_type":"date","api_name":"Stage_Updated_At"},"message":"invalid data","status":"error"}]}

I tried setting it as date object and a few date string formats but none of them worked. Any help is appreciated.