How to apply to an entire page or menu

Hello,
I want to change the homepage of the site, and it’s menu, based on the time.
Shortcodes are ok in the content, but I want it at the php level so i can do like this if time_restrict_off{//code for displaying the menu in site's page.php} else {//code for displaying a different menu} fi
and, of course, the same for the home page.

So, during ‘open’ hours the visitor gets content a, but when in ‘closed’ hours, they get a different menu and a different main page (content b)

Is this possible?