Convert PHP date into javascript date format

Question

I have a PHP script that outputs an array of data. This is then transformed into JSON using the json_encode() function.

My issue

Answer 1

An improvement or simplification of @jeremyharris answer would be this one:

DateTime objects in PHP have the getTimestamp() format, use it and multiply the value by 1000:

getTimestamp() * 1000; 
?>

// JavaScript
let startTime = new Date(phpDateTimeStamp);