Age-calculator using plain html-css-js

What are you most proud of, and what would you do differently next time?

I tried to make js code as readable as possible but that made me write more lines of code. It is a mess now😅. I considered leap year input, empty input and etc...

What challenges did you encounter, and how did you overcome them?

Writing readable js code

What specific areas of your project would you like help with?

I would like to write js code which focuses on better readability. Check js code, run some function i implimented in console and see changes. I am eager to get more suggestions.