Upgraded DS3231SN Chip, Not DS3231'M'The DS3231SN is the TCXO high stability RTC, acurate time keeping, accurate I2C real-time clock (RTC) module with a temperature-compensated crystal oscillator (TCXO) improving long-term accuracy RTC maintains seconds, minutes, hours, day, date, month, and year information. Less than 31 days of the month, the end date will be automatically adjusted, including corrections for leap year. The clock operates in either the 24 hours or band / AM / PM indication of the 12-hour format. Chip temperature sensor comes with an accuracy of ± 3°C Save time and high precision addition. DS3231 RTC Module also has some other features that extend the system host of additional features and a range of options. The device integrates a very precise digital temperature sensor, through the I2C * interface to access it at the same time Please Must Note:Because it's not safty to ship the Li Battery via air mail, our DS3231 RTC Modules don't include battery. For batter