25 June 1965: cinema release of Dr. Who and the Daleks, starring Peter Cushing as eccentric scientist Dr. Who.
25 June 1966: broadcast of first episode of The War Machines; first appearance of Anneke Wills as Polly and Michael Craze as Ben. The Doctor and Dodo arrive in London, where Dodo falls under the influence of the computer WOTAN.
ii) dates specified in canon
25 June 1906, 25 June 2006: birth and death of Edward Grainger (in the 2006 anthology, Short Trips: The Centenarian, edited by Ian Farrington).
25-27 June 1993: some of the events of the 1994 novel No Future by Paul Cornell.
25 June 2010: Amy Pond starts her travels with the Doctor.