Typescript thinks getYear does not exist on type Date

That API is deprecated. Try getFullYear() instead.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/getYear

This feature has been removed from the Web standards. Though some browsers may still support it, it is in the process of being dropped. Do not use it in old or new projects. Pages or Web apps using it may break at any time.

The getYear() method returns the year in the specified date according to local time. Because getYear() does not return full years ("year 2000 problem"), it is no longer used and has been replaced by the getFullYear() method.

Change this line from

let year = date.getYear() + 1900;

to

let year = date.getFullYear();