As always, my memory is fairly suspect these days - but I'm fairly sure Clark says his birthday is February 29th in the Baron Sunday episode.

Here it is in the script:

Quote
SUNDAY:

No trick. I only made use of what was already in his mind. (he regards Clark) You're a... Pisces, right?

CLARK: Good guess. February 29th.

SUNDAY: Nineteen sixty... five?

CLARK: Close. Sixty six.
LabRat smile


Athos: If you'd told us what you were doing, we might have been able to plan this properly.
Aramis: Yes, sorry.
Athos: No, no, by all means, let's keep things suicidal.

The Musketeers