From Halopedia, the Halo wiki
2558 was a year in the 2550s in the 26th century. It was the year the UNSC Infinity begins Spartan-IV deployments to Requiem in operations referred to as "Spartan Ops," beginning the Second Battle of Requiem in early February. The Battle of Ealen IV takes place in early March, the Battle of Ven III takes place in early May, and the Battle of Oban takes place in mid-July.
Before October 23