 Liam/Angel was born in 1727 and turned into a vampire in 1753, as  established in "The Prodigal" (1.15), and he counts 1753 as his  birth year. Although he spent 100 years in a hell dimension due to  Buffys actions in _"Buffy the Vampire Slayer" (1997)_ (qv) episode  "Becoming: Part 2" (2.22), he does not count those years as part of  his lifespan and told Cordelia in "Dear Boy" (2.5) that he was 247.  Allowing for aging and assuming that he survived "Not Fade Away"  (5.22), he is now 253 years old.