Datasheet

As long as it has a coin cell to run it, the DS1307 will merrily tick along for a long time, even

when the Arduino loses power, or is reprogrammed.

Talking to the RTC

The RTC is an i2c device, which means it uses 2 wires to to communicate. These two wires

are used to set the time and retreive it. On the Arduino, the pins are 'fixed' to be Analog 4

and 5 for the built in i2c capability. This is a bit annoying since of course we want to have up

to 6 analog inputs to read data and now we've lost two. There is a way to use other

pins...however, the hardware is by default set up for Analog 4 and 5 so lets start with that

You MUST have a coin cell installed for the RTC to work, if there is no coin cell, it will act

strangly and possibly hang the Arduino so ALWAYS make SURE there's a battery

installed, even if its a dead battery.