About waking at 1:00 PM
One in the afternoon lands squarely in the post-lunch dip, the genuine circadian trough that most adults experience between roughly one and three. It is a good time to schedule an interruption, and a bad time to schedule anything demanding.
Leave the tab open
A browser alarm can only ring while its page is open. It does not have to be the tab you are looking at, and on a desktop it does not have to be the window in front — but closing the tab or quitting the browser stops it. For anything you genuinely cannot miss, set a second alarm on your phone as a backup. That is true of every browser-based alarm clock, not just this one.