I assumed the tag would be based on the start date of an event, however I have this code
{exp:calendar:events orderby="event_start_date" author_id="{member_id}"}
which shows all entries. When I add the date_range_start parameter
{exp:calendar:events orderby="event_start_date" author_id="{member_id}" date_range_start="today"}
no entries appear, even though there are two events with start dates in May, 2014.