Hope that helps.
Birthdate: 1881 (JKR), probably in July or August. This date supersedes Jo's statement in 2001 that Dumbledore was "about 150 years old" (Blue Nose Day) and fits better with the dates that appear in Book 7. Regarding his month of birth, Rita says that Dumbledore was “nearing” his 18th birthday when he left Hogwarts in June, but was still 17 when he met Grindelwald (DH18). Basically, at some point during Grindelwald’s stay at Godric’s Hollow Dumbledore turned 18, so the month of his birth appears to be July or August.