I have a client with Odoo 8 and he get's this error when accessing the calendar form:
File "/opt/odoo/production/odoo/addons/calendar/calendar.py", line 1158, in get_search_fields
sort_fields['sort_start'] = browse_event['display_start'].replace(' ', '').replace('-', '')
AttributeError: 'bool' object has no attribute 'replace'
I changed the calendar view to week as default with mode="week". Then the error disappeared, probably the monthview goes wrong with the current date?