digitaltrix This software does what Google Calendar better known as GCal should have allowed from the start.
It allows you to search for multiple events or duplicates via text string/dates and clean them out in a single go (think email style).
This should be obvious and available in GCal but currently is limited to deleting an entire calendar.
GCal has a tendency to accumulate a lot of multiple even entries due to failed syncs with other programs.
Highly useful and site offers an online version to try out as well!