Insert Date & Time

wordpress functions
the_time() and the_date()
https://codex.www.ads-software.com/Function_Reference/the_time
https://codex.www.ads-software.com/Function_Reference/the_date

or do you mean the time when the page was called from the server?

<?php date(); ?>
https://php.net/manual/en/function.date.php

or time as in clock – ticking along?
would need a simple javascript – search the web, for instance ‘javascript clock’