Transactions can appear to be processed on the incorrect date if they are being made in different time zones than that of the gateway.
The date stamps are generally based on the servers' time zone where the transaction is procsesed. For instance, CyberSource is based on the west coast and uses Pacific time for the date stamp. Blackbaud Merchant Services processing is based on the east coast and uses Eastern time for the date stamp.
Example: A donor in New York makes a gift that is processed using CyberSource at 2:00 AM on 6/21. The gift will appear in BBPS as coming through on 6/21 but will appear in CyberSource for 11:00 PM on 6/20.