BeamerCola,
Do you have any working code that interfaces to the DS1307?
I am trying to the exact same thing, but as this is my first time ever using a micro controller I am having some troubles!
It would be a pain in the ass to do it with buttons.
You'd need a LCD or a few seven segment displays, a rotary switch (10 digits) and a 'next' button.
Or a up/down button for each value.
Easier just to send a unix timestamp over the usb port.
If your clock has a battery backup then you'll only need to do it once.