And here I thought maybe time zero would be the big bang, but alas, that is too celestial, so I guess January 1st, 1970 it is. Or whatever that is in the metric calendar (10 months per year, 10 days/week, 100 days/month)
We could use the birth date of that jewish prophet, except we'd still be off by a few years. Oh well, in a few centuries no one will care, and we'll just use Unix Epoch.