If you enjoy making clocks (and who doesn't?) here's an interesting take on the concept by Instructables user "oliverbogler". Instead of a typical timekeeping display they've used the Mayan "Tzolkin" calendar form, with hardware based on the usual word clocks that are popular. A "Tzolkin" calendar is:
... one of several calendars, and consists of 13 numbers and 20 day signs which appear in 260 combinations that rotate. In other words, with every change of the day the numer increases from 1 to 13 and then back to 1 again. Similarly the 20 day signs rotate.
Certainly something different and a neat addition to any family of timekeeping devices. With a little work and an IKEA frame the results are quite professional:
The most important part of any timing 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.