The date/time on the RSVP tab next to log contact ,when looking at a signup, doesnt appear to be taking into account the timezone of the event/user and is displaying events on the wrong day. Ive tested on user generated events, and events generated from the control panel. Both exhibit the same behaviour.
Updated - this is complete! Time zones for RSVPs are linked to the local timezone of your nation.
It looks like the events in your nation are in GMT + 12:00 Aukland time zone - but when you log an RSVP the time zones of the events are in UTC - which is causing the discrepancy. This is something we will definitely consider looking into but do not have a timeline at the moment.