The DS1307 is accessed via the I2C protocol. two wire I2C interface, Hour: Minutes: Seconds AM / PM, Day Month, Date Year, Size: 28x25x10mm, leap year compensation, accurate calendar to year 2100, 1Hz output pin, 56 Bytes of non-volatile memory available user

Features of DS3231 RTC ModuleSize: 38mm (length) * 22mm (W) * 14mm (height)Weight: 8gOperating voltage :3.3 – 5 .5 VClock chip: high-precision clock chip DS3231Clock Accuracy :0-40 ℃ range, the accuracy 2ppm, the error was about 1 minuteCalendar alarm clock with twoProgrammable square-wave outputReal time clock generator seconds, minutes, hours, day, date, month and year timing and provide valid until the year 2100 leap year compensationChip temperature sensor comes with an accuracy of ± 3 ℃Memory chips: AT24C32 (storage capacity 32K)I2C bus interface, the maximum transmission speed of 400KHz (working voltage of 5V)