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.
Goto Administration > Configuration and change the config-key: default.timezone
Valid timezone have to meet standards!
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.