Changing the Calendar and Timezone default
In general the timezone is configured in the user profile of each user, so changing the server timezone has no effect how to the users calendar for example.
However there are some circumstances where there is no user profile available.
Changing servers default timzeone for Emails and Invitations (display)
Goto Administration > Configuration and change the config-key: default.timezone
Valid timezone have to meet standards!
Changing first day in week for calendar from Sunday to Monday
Goto Administration > Configuration and change the config-key: calendar.firstday
The day that each week begins. The value must be a number that represents the day of the week. Sunday=0, Monday=1, Tuesday=2, etc.
Changing the default number of max participants of a conference room created via calendar
Goto Administration > Configuration and change the config-key: calendar.conference.rooms.default.size