The word "computer date" should be defined very clearly. And it can cause your design to fail if you don't decide on its definition.
According to me, date comparison should happen between two values which either reside at the same source or get generated by the same source. So in your case, for efficient calculations and to avoid timezone, incorrect time setup issues you should compare the dates in the database alone. i.e. both the dates - today's date and db date should be generated and compared in the database itself.
So in Access, you would do this:
=DateDiff(“d”, Now(), [tablename].[columnname])
Hope it helps