if column A and B are both formatted as dates:
=B2-A2
Format the result cell (C2) as General or Number.

Dates are actually stored as numbers that are incremented by 1 for each day,
so subtracting one date from another will always give you a number of days.

" wrote:

Is there a way to automatically calculate days since a particular date
(event)?
For example, if X event (in column A) happened on 1/1/06 and Y event
(in column B) happened on 10/14/07, how do I make column C = the
number of days between X and Y (column A and B)?

Thanks