I work with all the people around the world, mainly UK, Toronto, and San Jose. I used to manually calculate the time based on the time-zone difference. It is completely inefficient! This is even confusing when there is daylight savings in United State. Oh boy, I completely lost.
Now, this free Qlock Software solve all my problems. See my desktop below:
After you install the software, the next thing is to "Create Qlock" for the places that you want. What you need to do is to right click the icon on the lower right of the task bar, then select "Create Qlock". Select the City your wants and that's it. You will have something similar to my desktop. You can drag & drop and even resize the Qlock as you like. Try to play around with it and it is very user friendly.
Another thing, you can also set the alarm for each Qlock. Thought it will be useful to some of the people. I seldom use the alarm features as I don't really need it.