When did Christopher Eccleston leave Doctor Who?

Answer 1

David Tennant retired the role of The Doctor in Doctor Who to Matt Smith January of 2010. The two part special End of Time, with the first part airing December 2009 and the second New Year's Day 2011, marked the last two specials, and episodes, that David Tennant performed as The Doctor. A majority of the production crew had also retired from writing Doctor Who. The fifth series, with Matt Smith starring as The Doctor, has a new production and writing crew.

Answer 2

13 episodes: All of the first series since Doctor Who returned to our screens.

Answer 3

The last episode that features Christopher as the Ninth Doctor was aired on June 18th, 2005, so we can assume that he left the show in May/early June.

Answer 4

26 March 2005