An SMS bug appears to be plaguing some Windows Mobile 6.1 and 6.5 devices (and even non Windows Mobile phones apparently). Apparently, messages received after January 1st 2010 show up with the year as 2016. The issue has been reported on some HTC and LG devices so far.
There is no official statement or fix from Microsoft or affected device manufacturers. In the meantime, if you are experiencing this issue with your SMS, head over to WMExperts.com where they have a temporary workaround in the form of a CAB file.