The Chronological Defense Corps was a division within the Tholian Assembly that was charged with safeguarding the timeline. It had existed for centuries prior to the mid to late 24th century and was considered one of the factions in the Temporal Cold War alongside the Temporal Integrity Commission and Federation Temporal Agency as well as others.
In the 22nd century, the Corps had clashed with the Suliban Cabal over a 31st century Federation temporal displacement pod that was discovered by Captain Jonathan Archer of the United Earth Starfleet vessel Enterprise (DTI novel: Watching the Clock)