The DS3231 RTC High Precision Real-Time Clock Module is a low-cost, extremely accurate I2C real-time clock (RTC), it is more accurate than the ds1307 as this module is integrated with temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input and maintains accurate timekeeping when main power to the device is interrupted.
The RTC maintains seconds, minutes, hours, day, date, month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an active-low AM/PM indicator.
The AT24C32 provides 32,768 bits of serial electrically erasable and programmable read-only memory (EEPROM) organized as 4096 words of 8 bits each.
http://playground.arduino.cc/Code/Time
