1986 (production)

April

 * 8-11 April - Location filming for The Mysterious Planet took place. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 24-25 April - Studio filming for The Mysterious Planet took place at BBC Television Centre studio 6. (REF: Doctor Who The Handbook: The Sixth Doctor)

May

 * 10-13 May - Studio filming for The Mysterious Planet took place at BBC Television Centre studio 3. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 27-29 May - Studio filming for Mindwarp took place at BBC Television Centre studio 1. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * End of May - Around the time of Robert Holmes's death, Eric Saward resigned as script editor due to a disagreement with John Nathan-Turner over Saward and Holmes's plans for the final part of the Trial story arc; Nathan-Turner commissioned Pip and Jane Baker to write the final chapter.

June

 * 11-13 June - Studio filming for Mindwarp took place. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 15-16 June - Location filming for Mindwarp took place. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 23, 24 and 30 June - Location filming for The Ultimate Foe took place. (REF: Doctor Who The Handbook: The Sixth Doctor)

July

 * 1 July - Location filming for The Ultimate Foe took place. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 16-17 July - Studio filming for The Ultimate Foe took place at BBC Television Centre studio 1. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 30 July - Studio filming for Terror of the Vervoids took place at BBC Television Centre studio 3. (REF: Doctor Who The Handbook: The Sixth Doctor)

August

 * 1 August - Studio filming for Terror of the Vervoids took place at BBC Television Centre studio 3. (REF: Doctor Who The Handbook: The Sixth Doctor)
 * 12-14 August - Studio filming for Terror of the Vervoids took place. Unknown to most at the time, this would conclude Colin Baker's time as the Doctor on TV. (REF: Doctor Who The Handbook: The Sixth Doctor)

October

 * October - According to The Television Companion by Howe and Walker, at some point this month, Colin Baker was informed that his contract to play the Doctor was not being renewed.
 * 6 October - Around this time, BBC Controller Michael Grade approached the originator of Doctor Who, Sydney Newman, for ideas on how to revitalise Doctor Who. In a letter dated 6 October, Newman provided some ideas and suggested he be brought on board as executive producer of the series. He also attempted to be credited as the show's creator. Subsequent meetings, however, failed to result in Newman's return to direct involvement in the series.

December

 * December - The BBC announced that Colin Baker would not be returning as the Doctor in the next series.