++'s to tye for stating the answer which should always be considered first:P Why work so hard when the work has already been done for you?

unix epoch is good too as long as you don't have to do too much date interaction with users. I love using straight time() in my programs because I get everything I could ever want to know in one shot
If there is ever a chance to switch date formats, YYYYMMDD and unix epoch rank right up there.