The TARDIS said that her and the Doctor have been had 700 years of travel in time and space so assuming the Doctor was 909 in "the Doctor's Wife", he was around 200 when he stole it.

In "The Ribos Operation", the Fourth Doctor is 759 years old. "The Pirate Planet" follows on directly from "The Ribos Operation", and here it is stated that he  has been trvaelling in the TARDIS for 523 years. Thus, 759-523= 236.