This looks good. Arduinos by themselves aren't great at long-term time accuracy, so you should add a real time clock chip. Most people use the DS1307:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1235070596
this will also give you battery backup for the clock.
The code in the link above uses the ds1307 library directly, but I think it's easier to use the new Time library
http://www.arduino.cc/playground/Code/Time
and let it deal with the chip so I don't have to.
Good luck,
Chris