How to organize an action at night?

Question

JavaScript

I need to do a night action in the online store.
I see it as a banner appearing on the promotion page or a pop-up window with a promo code at a certain time of the day.
How can it be implemented? Preferably without getting into php.
Online chats somehow cope with similar functionality, but for other purposes.
Maybe some external javascript service?

Answer 1

var time = new Date();
if (time.getHours() === 23) {
  // do something
}

Answer 2

Well, you catch time, you prescribe a condition, and in its body a call to a modal window (for example). What is the problem?