Calendar duplicate cleaner

How matching works: the same UID plus the same start marks a twin, and so do different UIDs with identical start, end, all-day flag, a whitespace and look-alike tolerant title, and identical recurrence, excluded date, and extra date text. Times compare as UTC instants, all-day dates, or the same wall clock in the same named zone. The same moment written in two different named zones is not matched, because timezone definitions are not interpreted; those zones are copied through untouched instead. The survivor of a group is the copy with the highest sequence number, then the earliest in the file. Changed occurrences of recurring series carry a RECURRENCE-ID and are never removed, and neither are events with no readable start. The rebuilt file keeps every surviving line verbatim, alarms and custom properties included, and it is re-parsed before download so the kept count is measured rather than assumed. Nothing is uploaded and the original file is left as it is on your disk. To export from iCloud Calendar on a Mac, open File then Export, and pick Export.