Ages of Reclamation

The Age (or Ages) of Reclamation is a subject about which not much is known. The only reference is the beginning cutscene of Halo 2, where the Arbiter is on trial during the 9th Age of Reclamation. This could mean either that this is the ninth age, which happens to be the Age of Reclamation, or that there are several Ages of Reclamation, and this is the ninth, but no one knows which it is.

It is likely that they would be involved with the Covenant's annihilation of many species that were considered an "affront" to the gods, or their reclamation of Forerunner artifacts.

The events of Halo and Halo 2 take place during the 9th age of Reclamation, which existed from around the 3rd of February of 2525 to around the 21st of October of 2552, when the Covenant split up into a civil war that could very well scar the entire Galaxy for an eternity. It is possible that the eight other Ages of Reclamation came directly before the 9th, during which the Covenant were expanding their empire in their search for the Halos. The eight other Ages of Reclamation may have been created upon some new development in their search, though this is only speculation.

The 9th Age of Reclamation
At the time of Halo and Halo 2 the Covenant are in the 9th Age of Reclamation. It is possible that it began in 2525, when the Covenant first came into contact with humans. So far, the Age has contained a 27 year long war with the humans, the discovery and destruction of Installation 04, the threat of Heresy, the creation of a new Arbiter, the location of Installation 05, the threat of the Flood and the start of the Covenant Civil War.