The DS3231 is a low-cost, extremely accurate I2C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal.

The device incorporates a battery input, and maintains
accurate timekeeping when main power to the device
is interrupted. The integration of the crystal resonator
enhances the long-term accuracy of the device as well
as reduces the piece-part count in a manufacturing line.

The RTC maintains seconds, minutes, hours, day, date,
month, and year information. The date at the end of the
month 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 an AM/PM indicator.

Two programmable time-of-day
alarms and a programmable square-wave output are
provided. Address and data are transferred serially
through an I2C bidirectional bus.