From Halopedia, the Halo wiki
2506 was a year in the 2500s in the 26th century.
- ORION Project—the first attempt by the Colonial Military Authority to create and train teams of super-soldiers for covert military operations in the Outer Colonies—is deactivated. Though the soldiers were effective, their abilities fall short of original expectations, and they are far too expensive to develop and field. The soldiers in the program are reassigned to various special operations units.
These are events that are based around this year, and may not fall on this year specifically.
Around 5 years prior to September 8, 2511