Hi,
In this beta, to enable this option you have to add the data manually to the tables.
This will be fixed to next release.
You have to modify the option "calendar panel" in table "og_user_ws_config_categories", set "is_system" = 0
And you also have to add to "og_user_ws_config_options" a record with this values:
category_name = 'calendar panel'
name = 'start_monday'
default_value = '0'
config_handler_class = 'BoolConfigHandler'
is_system = 0
option_order = 0
dev_comment = ''
Then you can set this option at user preferences, calendar options.