Version:           Kontact 4.4 (using KDE 4.4.0)
OS:                Linux
Installed from:    Fedora RPMs

I am using the recently pushed 4.4 update from Fedora repos. I have had birthday data in my address book for forever, so it is possible the upgrades messed something up, but it seems unlikely given the scenario that is occurring.

I have some people in my address book. Specifically, there are two with birthdays as follows:

10 Mar 1989 -- Adam
25 Feb 1989 -- Bob
17 Feb 1987 -- Carl

I noticed today (Feb 25) that Kontact gave me a message saying Bob is 20 years old. Scrolling to March in the calendar, I find that it reports Adam's 20th birthday coming up. Clearly these are incorrect since it's 2010. Interestingly, I have some other birthdays not affected by this -- Carl is correctly reported as turning 23 in March 2010.

Doing further investigation, I find that if I scroll to Feb/Mar 2005, Adam and Bob are both listed as having their 16th birthdays, which is correct. But in 2006, they have their 16th birthdays again! Then in 2007 they turn 17, etc and from them on they are 1 year younger than they should be. (Carl has correct birthdays listed in each year I checked.)

So for some reason, some birthdays are broken between 2005 and 2006.