Using an Arduino (AVR) for accurate time

This is a good post that gets into timers on microcontrollers.  The author basically is using the clock cycle and interrtupts on the AVR to figure out how many seconds have gone by, so that way its telling “human” time correctly.  If you are into realtime this is very important (and basic) concepts to learn.

http://hackaday.com/2013/01/03/accurate-timers-with-an-avr/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+hackaday%2FLgoM+%28Hack+a+Day%29

http://www.seanet.com/~karllunt/interval.html