Handling Dates - Pre 1970

I'm working on a project that requires a profile system, and I need to store 3 dates in the 'profile' table date_joined, last_login and dob. For date_joined and last_login I will be using an int value, how ever for the dob field I don't think that will work as I anticipate some members to have birth dates before 1.1.1970 (such as me).

How do you guys get round this issue of storing/handling dates that are pre UNIX epoch?

TIA

Paul