1320

Before his attempt to change the outcome of the Battle of Hastings was thwarted by the First Doctor in 1066, the First Monk suggested that by supplying "a few hints and tips", jet airliners would be constructed on Earth by 1320. (TV: The Time Meddler)

Nyssa believed that she had visited Rhodes in 1320. The Fifth Doctor, however, identified the year as 1310. (AUDIO: Renaissance of the Daleks)

Behind the scenes
In Renaissance of the Daleks Nyssa says she was in Rhodes in 1320, while the Doctor later says it was 1310. Given the Doctor has a better knowledge of Earth's history than Nyssa, and the fact the real life Knights Hospitaller took over Rhodes in 1310, as is depicted, 1310 is the most likely date for this to be set.