How to create a countdown clock?

I was looking at a countdown clock of an email of a renowned company and tracked back the source. I came across the website https://countingdownto.com/create-countdown

Some of the good things I found:

• Creating a title
• Changing size and various parameters
• Smooth animation
• Embed or Share
• Email Countdown

Feel free to check the site and let me know your experience in comments.

Happy Coding. Keep Sharing.