I only add / edit / remove appts using Outlook on my computer - never on my iPad; because I am paranoid about the two not being perfectly in sync.
I just removed 2 (all-day) appts with client1 and added 3 new (all-day) appts with client2.
Before syncing, I went into iTunes INFO and (in the Advanced section) indicated (with a checkmark) REPLACE INFORMATION ON THIS IPAD - for both Contacts and Calendars.
After the sync was complete - I looked at the calendar on my iPad...and client1's appts are still there - and clients2 are NOT.
Thank you in advance for your time and attention.