What is the countdown timer for the site with the replacement of the content of the block at the end?

Question

Landing pages

Hello. Recommend the implementation of a timer for the landing, which for each new visitor will include the countdown of the time specified in the settings, and when the timer expires, the content of the block will change to the specified one.
That is, there is a timer that counts 5 hours, below it says "Buy a bucket for a promotion for 50 rubles, after the time expires, the bucket will cost 300" and below the timer is a block with the contents of the promotion (link to purchase, card, etc ..). At the end of the timer, this block changes to another one, with a different link, picture, and so on.