From Homestar Runner Wiki
Homestar's clock is kept in his bedroom. Homestar often mistakenly sets the alarm for 10 o'clock PM instead of 10 o'clock AM. At the end of Homestar Presents: Presents, it is used to display the number of minutes left until midnight on the 26th of the month. It runs off your computer's time and says "It's Over" should the time run out, a reference to Teen Girl Squad.
When watching the Flash file of Homestar Presents: Presents, if you right-click and select "Play" when Homestar's Clock is shown, it'll say "It's Over" right away instead of when the clock reaches 0.