Your only real ways to ghet out of this involve either flashing your bios (Gonna assume this is a bit above you though) or finding another Xbox/Friend with a modded box. From here: http://forums.afterdawn.com/thread_view.cfm/210562
1. There are some bios'es around that allow the chip to boot past the clocksetting. (do a search!). So how do you get that bios on your chip because you cant boot to a flash program or something? Well you need to have an external flasher.
It seems the m8 bios will take care for you of booting past the clocksetting. Or use the latest Xecutor bios
2. This is the more easy and newbie friendly strategy
-Get a friend with a modded xbox.
-Unlock his hdd with eeprom management from a slayer evo-x cd.
-Than, place his hdd in your xbox.
-Boot with your chip on.
-Now the xbox DOES find a dashboard when you boot in original mode and you can set the time in the msdashboard clock settings.
-Shut off xbox and remove your friends hdd
-PLace his hdd back in his xbox and lock it again
-Install your hdd
-(clock has been set) So boot up with slayer cd.
-Install normally whatever you wanna install