birthdate statistics?

[David Honig <honig@sprynet.com>]

If you learn someone's birthdate, have you obtained log2 (365 1/4) bits?
If you learn that someone was born in the first half-year, is this 1 bit?

I.E., Are birthdates truly uniformly distributed?  

Anyone thought about the applicability of cryptanalysis to 
identifying people from census info?  About identifying
Finns from their soon-to-be public health records.
(No, I don't want to do this, but how would you reason
about defenses against this kind of data mining?)