Age calculator app - React & Styled components

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

It feels good to have tried and tested out using styled-components. It's something I was curious about when I first started submitting solutions.

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

It'd be interesting to know if there is a more elegant way to handle the form validation on submission - there are a lot of if conditions to handle all the possible scenarios.