Gravity I2C RTC Real Time Clock (RTC) Module, SD2405 - 

Gravity I2C SD2405 RTC module an extremely accurate I2C real-time clock (RTC) with crystal compensation, inner chargeable battery. The SD2405AL can generates various periodic interrupt clock pulses lasting for long period (one year) and three alarm interrupts can be made by year, month, date, days of the week, hours and minutes, seconds. It also provides a selectable 32.768KHz~1Hz clock output for an external MCU. The product incorporates a time trimming circuit that adjusts the clock with higher precision by adjusting any errors in crystal oscillator frequencies based on signals from the CPU. A 12-bytes general SRAM is implemented in the SD2405AL.