2543

2543 was a year in the 2540s in the 26th century.

February

 * Preston Cole records his final entry in his personal log.

March

 * March 6: The Battle of 18 Scorpii takes place. UNSC forces are saved by Insurrectionists.
 * March 9: Vice Admiral Preston Cole contacts Admiral Dale Kilkin at UNSC Central Command Reach Logistics Office requesting a series of requisitions, transfers and favors.
 * March 18: Dr. Catherine Halsey finds her journal after it being lost for almost 6 years.

April

 * April 11: The Battle of Psi Serpentis starts with 's reconnaissance.
 * April 18: The Battle of Psi Serpentis, later known as Admiral Cole's Last Stand, takes place.

July

 * July 28: A day of mourning is proclaimed by the UNSC following the apparent death of Admiral Cole.