The drive to have all your clocks set to exactly the same time can be difficult, however not impossible - and demonstrated by Brett Oliver with his master clock system. Brett has modified a large analogue clock with an LCD and circuitry to pass timing pulses to secondary clocks.
The pulse and time data is shown on a large LCD, and for our readers within range of the DCF77 atomic clock transmitter in Germany the master clock receives the accurate time data from that transmitter. Brett has provided the required circuitry, Arduino sketches and some detailed images of the clock assembly, which is shown operating the following video:
If you need an accurate real-time clock IC for your own master clocks, consider our RTC: module based on 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.