To subtract weeks from a date:

To subtract any number of weeks from JavaScript date object. first create a JavaScript date object (you can pass  also desired date in date object) then only subtract you need to subtract number of days from date object

   currentdate = new Date();
   totalWeeksToSubtract = 2
   currentdate.setDate(currentdate.getDate() - totalWeeksToSubtract * 7);

To use calculate date difference between two dates in months the following code may help you

	var currentdate = new Date();
	var oldDate = new Date('2022-02-17'));
	let monthsDiff;
    monthsDiff = (currentdate.getFullYear() - oldDate.getFullYear()) * 12;
    monthsDiff -= oldDate.getMonth();
    monthsDiff += currentdate.getMonth();
   
   console.log(months)