Nothing more useful than having a watch on hand to answer when someone asks us what time is it? Our first challenge consists on creating two clocks (analog & digital) that run in the browser.
In an alternative scenario, imagine that you are part of a project in which you work with people from the east and west coasts of the US so, when coordinating a team meeting, it is necessary to keep in mind the working hours of all locations. Can you create a clock that simultaneously shows the time of California, Argentina and New York?