Absolute Time

According to the Celestial Intervention Agency's A Sourcebook for Field Agents, Absolute Time was the state of time on the planet Gallifrey, a base line against which all other time could be reckoned. The Gallifreyan time line was constant, at least as far as TARDIS use was concerned.

The concept was not just a convenient base line for TARDIS travel. The space-time vessels were designed in such a way that they could not penetrate Gallifrey's past, nor could any TARDIS travel into Gallifrey's future, for the present day on Gallifrey was an immovable temporal barrier for all TARDIS travel.

By nature, a TARDIS was from the current day and would move with the timestream as it aged even if it was outside of time for the most part. Thus, it could always return to Gallifrey after it left or as much later as it had spent in subjective time. A TARDIS could not return before it left, nor could it penetrate the temporal barrier into Gallifrey's future any further than the present day no matter where it was.

TARDIS devices were prohibited from entering Gallifrey's past for the protection of the history that created them in the first place, the same reasoning as was behind the First Law of Time. At the time of publication, the Time Lords themselves did not know the reason for the temporal barrier into the future, and a number of theories were put forth concerning its existence. Some temporal physicists considered it to be artifically created and maintained by some civilisation in the future, theorised to be the future Gallifreyans themselves. Most scientists, however, believed that it was tied up with an unchangeable rule of time. (PROSE: A Sourcebook for Field Agents ^[+]Loading...["A Sourcebook for Field Agents (novel)"])