College Entrance Exam Countdown Timer Accurate to Seconds

         Set the middle button as a status adjustment button and write in the program that when the button is pressed, the status +1 is set. A total of eight statuses are set. Status 0 displays the current time and is used to check whether the time is correct. When the status is 1, use At the time of changing the "year", in state 1, when the "+" button on the right is pressed, the year +1, similarly, when the "-" button on the left is pressed, the year -1, state 2 (adjust the month) , status 3 (adjustment day), status 4 (adjustment hour), status 5 (adjustment minute), status 6 (adjustment second) are the same. When state 7 is reached, a countdown is displayed. It is written in the program that when state >= 8, state = 0 is defined, that is, there are only eight states from 0 to 7.
         Arduino premium, use w806 development board instead temporarily.
         If you don’t know how to program, use domestic graphical programming software (http://www.linkboy.cc/).
         Created by a high school student.
         The programming software is easy to operate. You can only change a few values ​​to achieve other goal countdowns (high school entrance examination, postgraduate entrance examination, public entrance examination, etc.)