DS3231 I2C Real Time Clock Module with AT24C32 Memory

A low cost, accurate I2C real-time clock. with an integrated 32K AT24C32 EEPROM.
Supply voltage 3.3 V to 5.5 V
A coin cell battery holder allows fitting of a LR2032 rechargeable cell to provide a non-volatile backup facility.
2 programmable time-of-day alarms, a temperature sensor, and 32.768 kHz signal output pin.
The AT24C32 EEPROM can be used to add non-volatile data storage to your project.

Features
I2C communication - the default addresses - 0x57 (eeprom) & 0x68 (rtc).
Can be cascaded with other I2C devices
Two calendars and alarm clock
Two programmable square-wave outputs
Real time clock generator for seconds, minutes, hours, day, date, month, and year timing
Valid until 2100 with leap year compensation
Memory chip: AT24C32 (32 Kb storage capacity)
On-chip temperature sensor with an accuracy of ±3 ℃
I2C bus interface maximum speed: 400 kHz
Size: 38 x 22 x 14 mm

Note - Removing the on-board diode to prevent trickle charging will allow the use of CR2032 non-rechargeable cells - thanks to Simon John for the tip.

Arduino alarm clock project available here.
Memory IC datasheet here.