How do I merge multiple calendars into a single calendar in BusyCal?
You can merge multiple calendars into a single calendar by exporting calendar A and importing it into calendar B.
You'll find more info here:
https://support.busymac.com/help/70618-exporting-importing-and-merging-calendars
Merge Local with iCloud Calendar
You can merge multiple calendars into a single calendar. In this example, here is how you would merge the local Work calendar with the iCloud Work calendar:
Export the local Work calendar under On My Mac by selecting it and choosing File > Export, and save it to your desktop.
Delete the local Work calendar under On My Mac by control-clicking it and selecting Delete.
Double-click the file you exported in step 1 to import it. When prompted, choose to import the events into the Work calendar on iCloud.
Remove duplicates by selecting Help > Find Duplicates, and deleting any duplicate events that are found.
Repeat this process for each of your local calendars under On My Mac until you have merged them all with iCloud and there are no local calendars remaining.
Merging iCloud Calendars
You can merge multiple calendars into a single calendar. In this example, here is how you would merge the iCloud Home calendar with the iCloud Work calendar:
Export the iCloud Home calendar by selecting it and choosing File > Export, and save it to your desktop.
Delete the iCloud Home calendar by control-clicking it and selecting Delete.
Double-click the file you exported in step 1 to import it. When prompted, choose to import the events into the Work calendar on iCloud.
Remove duplicates by selecting Help > Find Duplicates, and deleting any duplicate events that are found.
Finding and deleting Duplicate Cards
You can merge multiple calendars into a single calendar. In this example, here is how you would merge calendar1 into calendar2:
Export calendar1 by selecting it and choosing File > Export, and save it to your desktop.
If you need to, delete calendar1 by control-clicking it and selecting Delete.
Double-click the file you exported in step 1 to import it. When prompted, choose to import the events into calendar2.
Remove duplicates by selecting Help > Find Duplicates, and deleting any duplicate events that are found.