TZClock is a small desktop clock program that you can view the worldwide time by setting the timezone,have multiple clocks in same desktop,set alarm clock,change the font and background color,set hour marks,change the clock size and so on.
TZClock’s Downloadpage provides the deb package:http://www.tzclock.org/download.html
Once you installed tzclock,you can open it from Applications->Accessories->TimeZoneClock
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System->Preferences->Startup Applications,Add–>type /usr/bin/TzClock in command area.