Calendars are to specify the standard holidays and the mandatory holidays allowed. To manage the Calendars go to Admin > Settings > Calendar sets. Each standard holiday calendar set or Mandatory holiday calendar set holds the next 4 or more years of calendars. One calendar set should be added for each different country or territory with different standard holidays with in it. The calendar set should be assigned to the appropriate employees by going to People > employee name > Person (dropdown menu) > Work and change the 'Working year' field.