BBMS and OLX transaction dates do not match

We are running into a problem with dates on gifts that come in late evening and early morning. For example, I get a confirmation email dated January 1 saying I have received a donation with a gift date of December 31. When I open the transaction to process it in OLX, the Details tab shows that the transaction date is January 1. If I log into BBMS, I can also see there that the card was charged on January 1. So why is the gift date on the confirmation email different? This email also went to the donor, who is now expecting a tax receipt for December 31. You can imagine the types of problems this creates, both with the donor's recordkeeping and our accounting.