Required files
icalendar/conversions
meta
hash_attrs
icalendar/base
icalendar/component
icalendar/calendar
icalendar/component/event
icalendar/component/journal
icalendar/component/todo
icalendar/component/freebusy
icalendar/component/timezone
icalendar/component/alarm
icalendar/parser