Hi. I noticed the XFCE Panel Clock Applet shows a completely wrong date here (Yesterdays my clock went wrong too), today it was showing me it was Monday 11th while the UNIX command "date" showed the correct one (Tuesday 12th). Workaround: Use the xfapplet-Plugin and the Gnome Clock Applet.
I confirm, the bug exists in 4.6.1.
Changed the code slightly to be the same as orage. Hopefully fixed in the next release, please reopen if it's not.