http://www.cadfamily.com/downinfo/300912.html

When the file being imported into Aspen Bulk Load has a day that differs fromthe current date where the user is importing, Aspen Bulk Load will ask tochange the time to midnight of the current time zone, but it does not adjustthe date. This causes the import date in Aspen Bulk Load to be off by one dayfrom the intended date.
This causes Aspen Bulk Load to fail to find existingdefinitions because it is looking one day too early. So it tries to add thedefinitions (instead of the desired modify), which results in validation errorsdue to existing definition.