Valhalla wall Easter egg

Previously in Halo 2, if one were to change their date and clock on their console, one would find different signs for each date replacing the original "No Swimming signs" in Zanzibar. The same can be achieved in Halo 3, as Valhalla has different messages located on the Forerunner Wall.

These can be accessed simply by changing the date on your Xbox 360.
 * January 1st (New Year's Day): Make Love Not War
 * October 31st (Halloween): A grave stone that says RIP
 * July 7th (Bungie Day): Seventh Column Symbol
 * July 4th: BBQ at Bob's House
 * November 11th (Veteran's Day): Killroy Was Here
 * May 5th (Cinco De Mayo): Toady Was Live!
 * December 25th (Christmas): A diamond with an X through it
 * April 22nd (Earth Day): A skull with a recycling sign