Old Time

The Old Time refers to the time on Gallifrey before Rassilon had created the Time Lord civilisation. In this time, Rassilon fought the vampires throughout the Universe (TV: State of Decay) and with Omega created the Eye of Harmony (TV: The Three Doctors), validium (TV: Silver Nemesis), and the Hand of Omega. (TV: Remembrance of the Daleks)

Gallifreyans had the ability to reproduce during the Old Time. When the Pythia cursed them with infertillity, they created Looms. (PROSE: Lungbarrow)

Lady Peinforte threatened to reveal the Doctor's secret "from the Old Time". (TV: Silver Nemesis)

The Doctor told the Mi'en Kalarash the he was afraid of the old time, that he remembered it and feared it's return. (AUDIOThe House of Blue Fire)

There is speculation about if this secret may be the nature of the Doctor's birth, as revealed in TV: Doctor Who by the Doctor. Russell T Davies, in an earlier script for TV: The End of Time, would have discounted this idea by having the Doctor say it was a "48-hour bug." (Doctor Who Confidential)