What software would change birthdates in a Contact - in a chain of Domino, Traveler, Windows Mobile and Outlook?

I have a strange problem with some of my Contacts with birthdates. I notice the problem first on the Windows Mobile 6.1 device (a Treo Pro), where I see birthdays adjusted by one, and some times two days.

The Treo Pro is synchronized via Lotus Traveler 8.5.0.0 to a Domino 8.5 server. To make synchornization issues even more hard to pinpoint, the Treo Pro also synchronize with Exchange 2003.

So, has anybody experienced something similar?