Mobile first Age Calculator - using CSS Flexbox and JavaScript

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

I'm proud of to complete different challenges every time. I would like to design multi-step form next time.

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

I'm stuck on DOB calculation for a hour, Then I go through again to get closer about formula.

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

DOB Formula