I'm using ST Microelectronics M41T11, which has a century bit.  Its
I2C.  You have to add your own watch battery and crystal, but power
switching is internal.

They have a web site, but I can't recall the URL.

------------
Barry King, KA1NLH
Engineering Manager
NRG Systems "Measuring the Wind's Energy"
Hinesburg, Vermont, USA
barry@nrgsystems.com
"The witty saying has been deleted due to limited EPROM space"