AVR based parking system - Simple Arduino Based Automated Parking Lot System - page 22

Modify time
Three push buttons ( setup , up and down ) are used to modify the time or select one of
the 17 screens to be displayed. These keys are connected to external interupt2, 0 and 1 re-
spectively.
By depressing setup push button, the content of set variable is increased one unit and if
we are in the main screen, each time that this key is depressed the following parameters can
be modified.
Hour, minute, second, day of week, day, month, year.
Each of the above parameters can be increased or decreased by up and down keys.
If the up or down pushbuttons are depressed without setup pushbutton, then the LCD
displays the state of each parking slot (1 to 16) or the main screen (17).