i've found one small issue.
when the time of an event has arrived and you change the time zone it will disappear even your are stil between start and end time.
e.g. at "BERLIN GTM+2" an event at 9:00 is scheduled. if i change the TZ to "MOSKOW GTM+4", the even will disapear at 11:00, in "GTM+2" i will still be visible till 10:00.
the times are displayed correct at any time and TZ, so it seems only to be the condition for "now" events ( event_end_time could be the problem, as it's not handled like the event_start_time )

cheers
jens