Old Time
The Old Time refers to a time on Gallifrey before Rassilon had created the Time Lord civilization. In this time, Rassilon fought the vampires throughout the Universe (DW:State of Decay) and, along with Omega, created the Eye of Harmony (DW:The Three Doctors), validium (DW:Silver Nemesis), and the Hand of Omega (DW:Remembrance of the Daleks).
According to a possibly apocyrchall source, Gallifreyans had the ability to reproduce during the Old Time. They were cursed with infertillity and forced to create Looms. (NA:Lungbarrow)
Lady Peinforte threatened to reveal the Doctor's secret "from the Old Time". (DW:Silver Nemesis)
There is speculation about if this secret may be the nature of the Doctor's birth, as revealed in DW:Doctor Who: The Movie by the Doctor. Russel T. Davies, in an earlier script for DW:The End of Time, was going to discount this idea by having the Doctor say it was a "48-hour bug." (Doctor Who Confidentail)