From Halopedia, the Halo wiki
- February 19: As part of Project CHRYSANTHEMUM, the SPARTAN-IIIs of Gamma Company begin their week-long augmentation process on the UNSC Hopeful in Sector K-009 folllowing its departure from Reach.
- February 27: The Hopeful returns to Reach following the Spartans' augmentation procedures.
- Before May, the CAS-class assault carrier Enduring Conviction, led by Let 'Volir, faces against the UNSC. During the battle, the Enduring Conviction performed impressive evasive maneuvers.
- May 8: Dr. Catherine Halsey undergoes the Hemley & Aubourn Behavior Analysis; the results make ONI increasingly wary about her reported unreliability.
- November 24: Mark V[B], the initial production model of the Mark V MJOLNIR armor, enters service.
- December 22: The Car & Pilot Magazine releases its December 2551 Edition. This includes a review of the new 2553 edition of the Civilian "Hog".
- Pawel Czernek enters active service with the UNSC Marine Corps.
- John Tippett enters active service with the UNSC Marine Corps.
- Concord is attacked by the Covenant; the colony survives largely intact. The Venator MJOLNIR [GEN1] variant gains prominence in the attack.
- Gray Team is deployed on a mission against a Covenant facility within humanity's former territory.
- The Battle of Meridian takes place. Meridian is glassed and Chalybs Defense Solutions facilities on the moon are abandoned. The Covenant discovers a Luminary on Meridian that leads to Earth.
- The UNSC Iroquois begins construction.
- Veta Lopis's mother dies.
- Halo: Ghosts of Onyx, page 101
- Dr. Halsey's personal journal, February 20, 2551
- Dr. Halsey's personal journal, February 27, 2551
- Halo Wars 2 - Phoenix Logs: Rise of Atriox III
- Data Drop 3
- Halo Encyclopedia, page 94 (2011 edition)
- Bungie.net: Bungie Weekly Update, 1/29/10
- Bungie.net: AMG Civilian Hog Review
- Halo 4, MJOLNIR/Venator armor description
- Halo Waypoint - Canon Fodder: Bits & Pieces
- Halo Waypoint: Catalog Interaction
- Halo 2: Anniversary, Terminal 1
- Halo Mythos, page 82
- Halo: Last Light, page 365 (Google Play edition)