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
 * April 22nd (Earth Day): A skull with a recycling sign
 * May 5th (Cinco De Mayo): Today Was Live!
 * July 4th: BBQ at Bob's House (This is a reference to Marathon in which you kill BOBs or BOB-B-Qing)
 * July 7th (Bungie Day): Seventh Column Symbol
 * October 31st (Halloween): A grave stone that says RIP
 * November 11th (Veteran's Day): Killroy Was Here
 * December 25th (Christmas): A Christmas light