PCF8523 - RTC Module with Calendar
The PCF8523 is a CMOS Real-Time Clock (RTC) and calendar optimized for low power consumption. It uses the I2C interface for data communication. Timer and alarm functionality is available to generate wake-up signals on an interrupt pin. Fine-tuning of the clock is possible due to the presence of an offset register. The PCF8523 has a backup battery switch-over circuit, which detects power failures and automatically switches to the battery supply when a power failure occurs.
For a detailed look at the specifications, refer to the datasheet: https://www.nxp.com/docs/en/data-sheet/PCF8523.pdf