Imperial Dating System - Chronostrife: Not long after the Ultramarines Primarch Roboute Guilliman's resurrection in 999.M41 as the lord commander of the Imperium and Imperial Regent, he launched the Indomitus Crusade to push back the encroaching forces of Chaos that had been unleashed across the galaxy after the birth of the Great Rift.Even as he made war, the primarch attempted to grasp the events of the ten Terran millennia that had passed since he had fallen during the Battle of Thessala to the Daemon Primarch Fulgrim.He was dismayed to find that much of Humanity's history had fallen afoul of superstition, fanaticism and hearsay during his absence. If anything, the state of Mankind's knowledge was worse than it had been during the Unification Wars, when the Emperor had unified Terra before the Great Crusade. Much of Terra's ancient history, painstakingly pieced together by the Remembrancers of Guilliman's own time, had been lost again.The primarch was determined to make a full and accurate accounting of the Imperium's fragmentary and often contradictory history, and so he commissioned the formation of a new organsation -- the Logos Historica Verita. It was charged with the daunting task of discovering, collating and cataloging thousands of standard years of Human history that had been lost or was woefully inaccurate due to superstition, suppression or purposeful obfuscation by the High Lords of Terra through such devices as Edicts of Obliteration and the existence of those crimes against truth known as the Historical Revision Units.The task of compiling a full and accurate accounting of the history of Humanity was a monumental and nigh-impossible task, compounded further by the fact that even the Imperial Dating System was woefully inaccurate.As the primarch digested thousands of standard years of history recorded upon every device conceivably employed by Mankind, he had come to learn of the Chronostrife of Terra, a bitter, ongoing internal war within the Ordo Chronos over the Imperium's dating system. What he read made him despair. Not even his father's calendar had survived the millennia intact.During the Great Crusade and the Horus Heresy, the standard 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.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's first phase drew to a close some dozen Terran years after his awakening, Guilliman 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; he had instead found there was none. It was something else that would ultimately require his personal attention to repair.The problem faced by Guilliman was that after the opening of the Great Rift, near every active Imperial war zone had to devise and reinforce its own chronological system. Even had the Imperium of Man not been split in half by the massive Warp rift, the sheer interstellar distances it covered prohibited any accurate reflection of time and space.Despite the flexibility of the "check number" system of old outlined above, pioneered at the time of the Great Crusade, where the first digit of each timestamp indicated its veracity, it became easy for dates and times to lose all meaning between star systems. Guilliman finally resolved the problem after a long conference with his historitors and the mysterious organisation of the Ordo Chronos. He decreed that a single logic could no longer be applied to time and space within the Imperium.Through the senate of the High Lords of Terra he made his theory and resultant process into law. There could no longer be a unified Imperial calendar with so much temporal distortion occurring across the galaxy. Even though the rift's temporal warping effects might not have reached the furthest spinward planets at the galaxy's fringes, its psychic echoes -- and the lack of the Astronomican that resulted -- were still felt profoundly on those worlds.Therefore, each sub-section of the Imperium would have to look to its own chronology, and use the coming of the Great Rift in that sector as its overarching reference point. The Cicatrix Maledictum became the defining point of the new era.This new system in practice by one world is outlined below.