This is a digital RTC - Real Time Clock and an EEPROM made specifically to be used with the Arduino, Raspberry Pi and all other general-purpose microcontrollers which support the I2C interface. The RTC can be used to store and retrieve the current time, while the EEPROM offer 32 kb of storage space which can be used for data logging. The RTC will use its inbuilt battery to keep time even when the Arduino or the external microcontroller is powered off. Similarly, the EEPROM saves its data even after a power off. This makes this module perfect for a time keeps and data logging.
The module uses the DS3231 IC for timekeeping. The DS3231 is a low-cost, extremely accurate I2C real-time clock (RTC), with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. It maintains time as seconds, minutes, hours, day, date, month, and year information. When there are less than 31 days of the month, the date will be automatically adjusted, including corrections for leap year. The clock operates in either 24 hours or 12 hours with AM and PM indications. The RTC works on external power when available and which too uses the onboard battery power supply when the external power supply is turned off.
The DS3231 is one of the best RTC available and offers the highest accuracy with the least power consumption. It can keep time using a single Cr2302 battery for years with the least variation.
Since this is a very popular board, Arduino libraries, sample codes, example projects, and tutorials are available on the internet.
Note: Battery Not included
1 x RTC Real Time Clock + EEPROM Module DS3231 AT24C32 for Arduino