2509

2509 was a year in the 2500s in the 26th century.

Unknown

 * By this year, many rebel cells had combined under the leadership of Robert Watts, proudly referring to themselves at the United Rebel Front.
 * The M850 Grizzly enters service with the UNSC.

Circa 2509
These are events that are based around this year, and may not fall on this year specifically.
 * Two years after Catherine Halsey met Elias Carver: Dr. Elias Carver commits suicide.