1)

• I create event with invitation to User1, start time is 7:00 CET
  -> User1 receives mail-invitation, all is fine
• I change start time of that event
  -> User1 receives update-mail-invitation, ICS attachment with event is fine, but Start and End time in text body of that messages are written in GMT. I think
  they was written in time zone of Organizer in the past (what I consider for better).

2)
I have the impression updated events received from outside systems are not updated well on SOGo server.

• I receive (by e-mail) event invitation from outside calendar system, I accept it
  -> it is correctly inserted into my SOGo calendar.
• then I receive updated event invitation (start time changed), I accept it
  -> Event window in Mail module offers me always all "Accept, Decline and Delegate" after my acceptation - but "Accept" would be not displayed after that
  -> Event in my calendar was not updated, it has original start time always.