The Ordo Chronos was one of the Ordos Minoris of the Inquisition that operated within the Jericho Reach. This mysterious and incredibly obscure Ordo was formed to investigate the potential ramifications of potential time travel through the Warp, particularly the potential for deliberate manipulation of this phenomenon. Details on what the Ordo found in their investigations are virtually nonexistent as the entire organisation disappeared from the face of the galaxy, taking their secrets with them. It is not known how or why this occurred, or if it was voluntary on behalf of the Ordos or not, though whispers of the involvement of dark technologies, long forbidden, have surfaced over the centuries since this mysterious incident. However, by the time of the early 42nd Millennium, the Ordo Chronos was known to be active once more, having either been reconstituted with a new membership or having returned from wherever it had gone.
Few have ever heard of the Ordo Chronos, even amongst the senior ranks of the Inquisition, and still fewer have any inkling as to its mission. It is generally believed that this particular Ordo came into being as a result of the study of the effects of Warp travel and the passage of time. Due to the unpredictable nature of Warp travel, it has been known that occasionally a vessel will be becalmed in the Warp. By the time it manages to extricate itself from the Immaterium the crew will have experienced the passage of mere solar months, while in the material universe many standard centuries may have passed. Far less common, however, are those occasions when a vessel has become embroiled in a Warp phenomena that has resulted in it being expelled from Warpspace at a point of time before it actually set out.
The Ordo Chronos, so it is believed, was established in the Jericho Reach in order to combat any temporal anomalies that might arise from these and similar events. This Ordo's Inquisitors feared that if such void travellers appeared in the past, they might somehow alter the proper course of events, potentially interfering with the fate of Mankind and the Emperor's intentions. Over several centuries, the Ordo Chronos investigated these instances thought to be related to all manner of temporal phenomena, their work eventually expanding beyond the original Warp-related events to others, perhaps even those of a deliberate nature.
Then, for some unexplained reason, the entirety of the Ordo Chronos disappeared. No one truly knows how many members the Ordo had, but in a single moment, every Inquisitor linked to this mysterious Ordo disappeared or went into hiding. Over the centuries whispered tales hint at the involvement of Renegade factions within the Adeptus Mechanicus and the pursuit of certain technologies long forbidden to that ancient brotherhood. No one living knows how or why they vanished, or if someday, their members may return. The Ordo Chronos remains the subject of legend amongst those few who know they ever existed. It is said that some of these individuals stay eternally vigilant against the doom such an event might presage for the future of Humanity itself, should they one day return.
By the time of the 42nd Millennium, the Ordo Chronos had either returned or been reestablished, as its members began an internal feud known as the Chronostrife once the resurrection of the Primarch Roboute Guilliman made clear that the Imperial Dating System itself had fallen deeply into error with the passage of the millennia.
By the first century of the 42nd Millennium, the Ordo Chronos was involved in an ongoing and bitter internal conflict over the Imperial Dating System, for the Emperor's calendar had not survived the passing of the millennia intact. During the Great Crusade and the Horus Heresy, the standard Imperial Dating System had provided some idea of the order of events over time, but like everything else the Emperor had created, the calendar had become degraded by both dogmatic adherence and thoughtless revisionism over the centuries. Various rival dating systems had evolved from the Imperial Standard, making a true chronicle of the human-settled galaxy almost impossible to construct. As the Indomitus Crusade drew to a close sometime around 111.M42, Roboute Guilliman, the Lord Commander of the Imperium and Primarch of the Ultramarines, calculated the current year by the five main factional variants of the Imperial Calendar to be anywhere between the early 41st Millennium and an entire millennium later, and that was leaving out the numerous lesser, more heretical interpretations. Guilliman had been hoping to find a solution to the Imperium's tortured dating system, but had instead found there was none. It was just one more item that would ultimately require his personal attention to repair.
- Codex: Inquisition (6th Edition), pg. 6
- Dark Heresy: Ascension (RPG), pg. 171
- Dark Imperium (Novel) by Guy Haley, Ch. 9 "Imperator Gloriana," pp. 96-97