[index.html] Events are from UTC times, not PST

Looking at e.g. http://data.githubarchive.org/2012-03-08-0.json.gz

All events within that dataset have timestamps from 
"2012-03-08 00:00:00 UTC" through
"2012-03-08 00:59:59 UTC".

The main page says the dataset should have been cut at midnight PST (-08:00), which, if true, would make the events have event.created_at from "2012-03-08 08:00:00 UTC" to "2012-03-08 08:59:59 UTC".