I had some free time today so I finally got around to allowing my Arduino to sync the DateTime over the internet using the wiznet module. It grabs the time from the NIST server which gives a response like this:
54964 09-05-13 21:01:33 50 0 0 14.3 UTC(NIST) *
From that it was a little bit of work figuring how to convert to unix time, but I got it sorted. The nice thing about using NIST is that it also indicates if it is daylight savings or standard time so the time will always be correct. No adjustment needed or watching for specific dates. I currently update the time every twelve hours. With the price of the wiznet module around $16 I think this trumps having a RTC because of the other things you can do with ethernet.
Currently, this is in a pretty large program on my Sanguino. If there's interest I could put together an example sketch that simply updates the time from NIST.