The RaspberryPi does not have a real time clock (rtc) so normally requires an internet connection to reset the time and date from a time server.
For my BirdBox 2014 project I need to be able to time-stamp files & data, but it would not matter if the system time was a few minutes out either way, so I have been considering the options.
One popular solution is to connect a small rtc board to the RaspberryPi. These boards are small, low cost, and include a lithium backup battery.
