DESCRIPTION:
The DS1307 is a low power, with 56 bytes of non-volatile RAM BCD code clock calendar real-time clock chip, the address and data transmission through the two-wire bidirectional serial bus, the chip can be seconds, minutes, hours and other information , the number of days in each month can be adjusted automatically. And there is a leap year compensation function. AM / PM flag determines clock work 24-hour or 12-hour mode, the chip has a built-in power-sense circuit, brownout detection and battery switching function.
 
FEATURES:
 
Module Feature :
DS1307 I2C real-time clock chip (RTC)
24C32 32K I2C EEPROM memory
Using LIR2032 rechargeable lithium battery (not included) with charging circuit. (Do not charge if used with CR2032!) 
Fully charged, it can provide 1 year lifetime
Compact design, 27x28x8.4mm
Leads to the a DS1307 clock pin, to provide the clock signal for the MCU
Can be cascaded to other I2C devices
 
DS1307 Feature :
Can account seconds, hours, minutes, monthly number of days, months, days of the week count with leap year compensation function. Record the year on line 2100
56 bytes of non-volatile RAM
Two-wire serial interface
Programmable square-wave output
Automatic power-down detection and switching circuit
In battery backup mode, power consumption is less than 500nA
Battery not included.
 
Resources: 
1. Interface DS1307 RTC Module with Arduino