Apple Script Question

Hi, im a Teachers assistant at my highschool for the tech department. Anyways me and my teacher have this on going prank war kind of thing and im trying to make a script that sets a custom screen saver (that i have bulit) to run on his computer at login on april 1st.so...

1st. is there a away i can make a cron script to activate on april 1st

2nd. how would i make the screensaver go in the login items

or better yet a quicktime movie in fullscreen at login, that might be easier