We need to improve the configure_cisco7970.pl script.
That script creates a file in /tftpboot/SEPxxxxxxxxxx.cnf where xxxx... is the MAC address of your phone. If you only have one phone, there will only be one SEPxxxxxxxx.cnf file.
Inside this file, are a variety of configuration settings... One of these settings is for date format, another is for time zone. I can't remember off the top of my head where the documentation for these settings is, but you can find it on the http://www.voip-info.org/