I’m not sure how long this feature has existed in Windows, but I just discovered it on Windows 7 and felt foolish for not finding it sooner. My customers are National, so I often have meetings in a time zone that I’m not physically located in. Sometimes, it helps to visually see the clock for different zones at the same time. Luckily, you can configure additional clocks in Windows 7!
By default, if I hover my mouse over the time in the task bar it will show me today’s date.
To configure additional clocks:
Now when you hover over the time in the task bar, it will show you the times in your additional zones.
Single clicking the time, will show you the clocks for each zone.