Auto update clock

When i switch between drives, the clock on suse stops at the time of the switch. How do i set it to update from a server that keeps the time, rather than an internal clock so it isnt always wrong?

Set to NTP via yast

Just an addition to clarify
Yast > Network services > NTP configuration > select now and on boot and then a sever close to you in the drop down list

/Geoff