Pi RTC (DS1307) The Pi RTC is based on the clock chip DS1307, it can provide a real-time clock(RTC) for raspberry pi via the I2C interface. Real-time clock of this module counts seconds,minutes, hours, date of the month,month, day of the week, and year with leap-year compensation valid up to 2100. The clock operates in either the 24-hour or 12-hour format with AM/PM indicator. If you want to keep this module timing when the Raspberry Pi is powered off, you need to put a 3-Volt CR1225 lithium cell in the battery-holder. Note The battery is not included. Features Support Raspberry Pi 2/ 3 B/B+ Zero Suport seconds,minuutes,hours,day of week,month, year Support 24-hour or 12-hour format with AM/PM indicator 56-byte, battery-backed, nonvolatile (NV) RAM for data storage Two-wire serial interface Programmable squarewave output signal Automatic power-fail detect and switch circuitry Specification Item Value Operating Voltage 5V Interface I2C I2C Address 0x68 Typical applications Any applications need Real Time on Raspberry. Pin Out Note RX/TX is not used in this module, but the 5x2 header takes up the RX/TX pin of the Raspberry Pi, so we bring the RX/TX out and come with a 2pin header.