The Appliance is the Webbrick Gateway pre installed onto a small fanless computer:

As delivered the appliance should be set to the UK daylight time zone (BST), although some early ones where set to GMT (the clock does not shift as clocks go back and forward). If it becomes neccesary to change the time zone then it is neccessary to login to a command prompt on the appliance to make the change.

It is assumed  that you have some experience of the Linux/Unix environment:

login and then:

cd /etc

rm localtime

ln -s localtime /usr/share/zoneinfo/Europe/London

Explore /usr/share/zoneinfo to identify the correct timezone for your locality. The gateway will need restarting so that it recalculates the sunrise and sunset times properly.

/etc/init.d/webbrick stop

/etc/init.d/webbrick start

 On early systems replace webbrick by HGA in the above.