I made the following list of the Doctors (minus eighth and war) listing the actors lifespan or current age, the years they were officially the doctor on television, their ages when they first appeared after their predecessors regeneration (obviously no regenerations before the first), their ages at regeneration and how long they were/are the Doctor. Why no eight or war? Because they appeared on TV once. That is also why I cut seven off at 1989, because there was a hiatus, and one appearance, followed by another hiatus. The show stopped being produced by the BBC in 1989 until 2005.
First Doctor
8 January 1908 - 23 April 1975 (67 years, 3 months, 15 days)
23 November 1963 - 29 October 1966 (55 years, 10 months, 15 days - 58 years, 9 months, 21 days)
2 years, 11 months, 6 days
Second Doctor
25 March 1920 - 28 March 1987 (67 years, 3 days)
29 October 1966 - 21 June 1969 (46 years, 7 months, 4 days - 49 years, 2 months, 27 days)
2 years, 7 months, 23 days
Third Doctor
7 July 1919 - 20 May 1996 (76 years, 10 months, 13 days)
3 January 1970 - 8 June 1974 (50 years, 5 months, 27 days - 54 years, 11 months, 1 day)
4 years, 5 months, 5 days
Fourth Doctor
20 January 1934 (85 years, 11 months, 18 days)
8 June 1974 - 21 March 1981 (40 years, 4 months, 19 days - 47 years, 2 months, 1 day)
6 years, 9 months, 13 days
Fifth Doctor
13 April 1951 (68 years, 8 months, 25 days)
21 March 1981 - 16 March 1984 (29 years, 11 months, 8 days - 32 years, 11 months, 3 days)
2 years, 11 months, 24 days
Sixth Doctor
8 June 1943 (76 years, 6 months, 30 days)
16 March 1984 - 6 December 1986 (40 years, 9 months, 8 days - 43 years, 5 months, 28 days)
2 years, 8 months, 20 days
Seventh Doctor
20 August 1943 (76 years, 4 months, 18 days)
7 September 1987 - 6 December 1989 (44 years, 18 days - 46 years, 3 months, 16 days)
2 years, 2 months, 29 days
Ninth Doctor
16 February 1964 (55 years, 10 months, 22 days)
26 March 2005 - 18 June 2005 (41 years, 1 month, 10 days - 41 years, 4 months, 2 days)
2 months, 23 days
Tenth Doctor
18 April 1971 (48 years, 8 months, 20 days)
18 June 2005 - 1 January 2010 (34 years, 2 months - 38 years, 8 months, 14 days)
4 years, 6 months, 14 days
Eleventh Doctor
28 October 1982 (37 years, 2 months, 10 days)
1 January 2010 - 25 December 2013 (27 years, 2 months, 4 days - 31 years, 1 month, 27 days)
3 years, 11 months, 24 days
Twelfth Doctor
14 April 1958 (61 years, 8 months, 24 days)
25 December 2013 - 25 December 2017 (55 years, 8 months, 11 days - 59 years, 8 months, 12 days)
4 years
Thirteenth Doctor
17 June 1982 (37 years, 6 months, 22 days)
25 December 2017 (35 years, 6 months, 8 days - 37 years, 6 months, 22 days)
2 years, 13 days
