import { DatePipe } from '@angular/common';

declare global {
    interface Date {
        transformTo(format: string): string;
    }
}

Date.prototype.transformTo = function(format: string): string{
    return new DatePipe('en-US').transform(this, format);
};

export {};

Results in the error:

Property "transformTo" does not exist on type 'Date'.

I've looked at several S.O. posts and everything looks right. When I have a Date intellisense know the extension method and what it expects. The vs code doesn't show an error. The error only occurs when running 'ng build'

Angular version: 9.1.11

Node Version: 14.8.0

NPM Version: 6.14.15