.getMinutes()

Called from an instance of the Date class, will return the minutes according to the local time.

myDate.getMinutes();

The return value of getMinutes() will only be an integer number between 0 and 59, meaning the minutes according to the local time.

To determine if it has been 15 minutes:

const today = new Date('June 25, 2021 13:15:00');

if (today.getMinutes() >= 15) {
  console.log('Hurry up, it has been 15 minutes!');
} else {
  console.log('Take your time, we still have time for it.');
}

// Output: Hurry up, it has been 15 minutes!