2521

2521 was a year in the 2520s in the 26th century.

October
October 15
 * Dr. Catherine Halsey records in her journal regarding the recent destruction of the after terrorists disable it, she also mentions how third generation Artificial intelligence recently became first operational.

Unknown

 * The Sniper Rifle System 99 Anti-Matériel is adopted by all branches of the UNSC Armed Forces because of its modularity and ongoing manufacturer support.