Age Calculator with some transition animations (JS/HTML/CSS)

First attempt at a Level 2 challenge, wasn't too hard but certainly a lot more work going into it! Just Vanilla JS, HTML/CSS.

My big question is how much time should a challenge/project like this be completed in? I didn't keep a good track of everything I did, but it took me roughly 3-4 days in my free time to implement everything, from the styling, creating and testing the calculation/logic, transition animations, final touches and documentation/commenting. It feels like it took longer than it should, mostly because I was trying to be a little bit extra, but what's a reasonable time estimate for something like this? Both from a junior to senior level would be helpful.

Also jumping back into JS after a break for awhile, used setTimeout() and setInterval() for a lot of the animations. Feels like it might have been more overhead with timing the delays and durations, as opposed to using async/await with promises, but maybe fine in this case?

Anyways, thanks in advance for checking out my submission and any comments! Let me know if there's anything else that seems to stick out!

Quick thanks to:

ApplePieGiraffe - Providing resources on using em/rem.

Vanza Setia - Some tips on container styling and when to use ID attributes.