In the time of the ultimate business era with smartphones and email, one person can be in communication with multiple people in multiple countries across the world. I would deem it rather beneficial to keep track of the different timezones in countries of relevance to you.
Cue the World Clock (I know, kind of generic) and its simple yet helpful interface. The idea is ridiculously easy. The center of the clock has 6 arms that can be placed to any time on the clock. The map behind the hands of the clock is a place to put a magnet on a country you wish to mark. The magnet’s color should correspond to the hand for the timezone you wish to label.
Now with one glance you can figure out the time of day for the countries that mean something to you!