Responsive Age Calculator using CRA, Yup and Moment.js

Hello everyone! I just completed my first FrontendMentor project and wanted to share my work here with everyone. There are a few things that I would like to improve, but I'm not sure how:

• the calculation algorithm that I created is not always accurate. While it shows the correct number of elapsed days, months, and years at times, there are occasions when it doesn't calculate properly. I've run several tests, but I haven't been able to identify why this bug persists.
• haven't been consistent with the naming of CSS classes. Perhaps, I should have used a CSS-in-JS library to make the process more systematic.
• the mobile version of the project doesn't look as polished as I would like it to.

If you notice other faulty stuff going on, please do not hesitate to share it with me too. Looking forward to hearing your feedback, folks!