Size: 38mm (length) * 22mm (W) * 14mm (height) 
Operating voltage :3.3 - 5 .5 V 
clock chip: high-precision clock chip DS3231 
Clock Accuracy :0-40 ℃ range, the accuracy 2ppm,  the error was about 1 minute 
Calendar alarm clock with two 
Programmable square-wave output 
Real time clock generator seconds, minutes, hours,  day, date, month and year timing and provide valid until the year 2100 leap year  compensation