If you move a calendar item in Outlook there is no Undo facility.

Had a case where a secretary accidentally dragged a calendar item in her
bosses calendar, and although she realised straight away, she didn't know
where she had moved it from. She had to contact the external people he was
meeting with in order to find out what the time the meeting was supposed to
be at.

[Haven't tested 2007 yet :-)]

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