Buffy's two birthdays

So I'm watching "I Robot; You Jane" and I'm up to the scene where Moloch scans the school records for info on Buffy. The screen shows a birth-date of 10/24080, but then when Moloch sends the data to Fritz, the birth-date has changed to 5/6/79. Ooops! *amused grin*

first Scooby pizza sighting & a hedonistic Giles

Okay,

I'm trying to work out when the first Scooby research party where they ordered in pizza happened. I've watched through "I Robot; You Jane" and haven't seen it yet. I'm wondering because for my Giles as the Big Bad story I'm making Giles hedonistic, one of the signs of which would be him not eating the pizza but ordering something for himself from one of the better local restaurants.

And while I'm on the subject, what other signs of Giles' hedonism can you think of? I've already got the idea of a killer car. He might dress slightly better but he also would feel the need to dress as well as the Council would expect him to so possibly not so much there. He's hitting on Jenny much more quickly. What else?

Thanks!