In the pilot, Clark was twenty-nine, if I remember it correctly. Lois was supposedly a year younger, which would have made her twenty-eight.
Actually, Lois was 26 (which she very acerbically points out to Lucy when she says she has no life), which would make Clark 27.
In later episodes, we learn that Lois was born in 1967 and Clark in 1966.
I always found it funny that Clark was older than Lois, because in real life, Teri was nearly 18 months older than Dean. (Her birthday is Dec. 8, 1964, and his is July 31, 1966.)
