How can I display multiple time zones on my Linux?

Hello everyone,
I am working online with clients from different countries. I always have to check the time of the respective client’s country before calling him. I want to see multiple clocks on my desktop to save my time. I have done this before on windows 7. But now I have to do it on Linux. I don’t know how Linux displays multiple time zones. If anyone has the better solutions then share it with me. It would be very helpful for me.
Regards
