Check that your WordPress site has the correct date. Go to ‘Settings > General’ and down below where it says Date Format, you should see todays date.
If this is incorrect then your Database is set up incorrectly with the wrong date/time and probably something your host needs to take care of. I’m not 100% sure how to fix it if that’s the cause as I’ve never seen that before.
Thanks for quick answer, Evan. General Settings was what I checked first of course but it seems OK 🙁
Actually, <<Next>> link goes to correct next month (August, 2014). As this calendar is not plain calendar and is linked with posts, I thought if it thought that I have some posts in 2003 January and that’s why it shows it, is it possible?