DS1307 I2C bus RTC chip, DIL08 package. Can be plugged into a socket on some Modtronix board to add a RTC.

• Real-time clock (RTC) counts seconds, minutes, hours, date of the month, month, day of the week, and year with leap-year compensation valid up to 2100
• 56-byte, battery-backed, nonvolatile (NV) RAM for data storage
• Two-wire serial interface
• Programmable squarewave output signal
• Automatic power-fail detect and switchcircuitry
• Consumes less than 500nA in battery backup mode with oscillator running