This Arduino Tiny RTC I2C module incorporates the DS1307 I2C real-time clock IC and the 24C32 32K I2C EEPROM storage. All of this in a tiny package of 25mm x 28mm x 8.4mm. It comes with a LIR2303 rechargeable lithium battery (NOTE! No include the LIR2303 battery in this product, just a LIR2303 battery holder), the RTC module can run for 1 year on a single charge.