merge calendars

Bill,

First, backup your Calendar using Calendar>File>Export>Calendar Archive...

Are you syncing with any other devices/services?

If not, just use Calendar>File>Export>Export... for Personal A. Save the exported copy to your desktop. Next double-click the exported file and you will be offered to create a new calendar or merge with an existing calendar. Choose to merge with Personal B. Then you can delete calendar Personal A.

Bill,

Since you are using iCloud, the same procedure I specified earlier should still apply. iCloud: Manually importing data from Calendar or iCal to iCloud Calendar will be helpful.