The calendar in my 2004 TL navigation systems always resets to January 2002. If I move it forward to today's date, it will return back to January 2002. In the past it has always kept the correct date.

 

In the 2 and 1/2 years since you posted this, you probably already have the answer by now. In case you didn't know or for anyone else reading this, it was due to a software bug. My 2004 Acura TSX is the same way and still is. My calendar defaults to a month in 2002 as well (I can't remember which off hand as I don't look at the calendar on my NAV system much.) The time is off as well but I can manually change it.
The date bug will never be fixed. More info here...

https://didhondafixtheclocks.com/