Responsive functional age calculator app with Html,Css and Javascript

I use my free account on front end mentor to test my front end skills and I already finished one problem before.(https://www.frontendmentor.io/solutions/responsive-newsletter-using-html5css-flexbox-and-javascript-oNvZwtj4fp).The age calculation in this project was a bit difficult as Javascript don't have a built function for it but I figured it out after doing some research. Feel free to give feedback about the improvement in this project and guide me about the best practices. Don't forget to like and rate my project out of 10