This Real Time Clock (RTC) is the most precise you can get in a small, low power package.

Communication is via i2c. The default address is 0x57.

The DS3231 library is installable directly from the Arduino Library Manager.

2032 Coin cell battery NOT included

Features

• Dimension: 38mm* 22mm * 14mm
• Weight: 8g
• Working voltage: 3.3 - 5.5V
• Clock chip: high-precision clock chip DS3231
• Clock accuracy within range: 0-40°, accuracy 2ppm, about 1 minute in error
• Programmable square-wave output
• Real-time clock, it can generate seconds, minutes, hours, day, date, month and year, and provide time until 2100, and with leap year compensation.
• Internal chip temperature sensor comes with an accuracy of ± 3°
• Memory chip: AT24C32 (storage capacity of 32K)