fix major timezone conversion bug

current code worked when server's time zone == EVENT_TIMEZONE

if it was not (example: server timezone = EST, EVENT_TIMEZONE = PST), then it would take the datetime.now() which was in local timezone, chop off the local timezone, and replace it with the EVENT_TIMZEONE.  however, this replacement is incorrect, as the local time is not converted into the desired timezone.

cherry-picked from Rockage branch
We already have a ``UTC`` global variable so adding this new global variable is unnecessary.  Also, by convention in the Uber codebase we tend to have global constants be capitalized.