Calculate an age from a hardcoded date of birth

I have no JS expierence but think this can be dome in HTML.

I have a nember of Peacocks

I need to be able to calculate the age of a peacock, the date of Birth would be entered in by me in the code and then I need the system clock to calculate the age, so it is always current.

The code is then being embedded into a 360 VR tour.

Any guidance please