The day that a building was built as a primary key?

Given the possibility that 2 buildings could be built on the same day, it doesn't sound like a good candidate.

Can you really build a building in one day? This sounds like something out of the Mythical Man Month. Most managers I have worked for are absolutely convinced that if one woman can make a baby in nine months then if follows that nine women can make that same baby in one month:)

you dont need it to be ap rimary key

have an autonumber as a key, but make the date field indexed as well. then you can decide whether you want to allow duplicate dates, and if necessaqry, you will be able to modify a date