How to build a countdown script?

Question

JavaScript

Good to everyone.
The problem is so trivial that it's not even a lot of shame. But you need to take a countdown script for 1 hour 01:00:00 of this kind that would calmly tell off the time and move it to another page.
Everything is quite simple, but it is not possible to make it work correctly and the time has changed.
Thanks to everyone who replies.

Answer 1

https://codepen.io/anon/pen/PQgKzX