As an interesting art installation, reddit user ewoolsey has created an interesting and huge world-time clock. Instead of a simple digital display, they have instead created a giant abstract map of the world based from a Mercator projection, with holes drilled through the surface to represent land mass.
The time is then displayed by using RGB LEDs behind the holes, where the colour of the light represents the time over that area. Thus over time a sweeping motion of vertical colour bands will represent the change in time across the world.
Apart from being a neat art installation, a smaller (or larger) version would be great in an office with various outposts or in the study of a travel enthusiast. Either way, you can find more details through the creator's project gallery. And for more, we're on facebook, twitter and Google+, so follow us for news and product updates as well.
The most important part of any clock project is the inclusion of an accurate real-time clock IC. Here at Freetronics we have the Maxim DS3232 real-time clock IC module:
Apart from keeping accurate time for years due to the temperature-controlled oscillator and having a tiny coin-cell for backup, it is very simple to connect to your Arduino project. A driver library allows your program to easily set or read the time and date. Perfect for clock projects, dataloggers or anything that needs to know the date and time. Furthermore it contains a digital thermometer and 236 bytes of non-volatile memory to store user settings and other data. For more information, check out the module page here.