This applet allows you to add multiple clocks to your Cinnamon system tray with different time zones.
Add the contents of this repository to:
~/.local/share/cinnamon/applets/worldclock@jordon
To display multiple time zones simply add the applet multiple times to your panel. Clicking on the applet will bring up the configuration screen.
Use something meaningful to indicate what time zone this clock is for, eg LON.
The GMT offset in hours, eg 11 for Sydney time during daylight savings, or "1.5" for +01:30.
Unfortunately due to the difficulties with date formatting in Javascript, I was unable to use a timezone code and automatically adjust DLS. If you have any genius ideas, please let me know!