DS1307 - RTC Module
The DS1307 serial real-time clock (RTC) is a low power, full binary-coded decimal (BCD) clock/calendar with 56 bytes of NV SRAM. It uses I2C for communication. The clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12- hour format with AM/PM indicator. The DS1307 has a built-in power-sense circuit that detects power failures and automatically switches to the backup supply. Timekeeping operation continues while the part operates from the backup supply.
For a detailed look at the specifications, refer to the datasheet: https://datasheets.maximintegrated.com/en/ds/DS1307.pdf