The shield includes 4 programmable buttons, labelled "A" to "D". These buttons are used to change the month of the calendar. When first booting up the device or when pressing the reset button, the display shows the current month with the current day highlighted with a red circle. Pressing buttons "A" or "C" will move to the previous or next months, respectively. Pressing button "B" will switch back to the current month.

The "D" button is used to move the calendar either forward or backward by one year. By default, the button will move to the same month in the next calendar year. However, if the previous month button "A" is pressed, then button "D" will instead move to the previous calendar year.  If button "B" or "C" is pressed for the current or next month, then button "D" will again move to the next calendar year. Press button "D" successive times to move forward or backward multiple years.

Status LED

The Metro M4 Express Airlift also comes with a single NeoPixel. This project uses the NeoPixel as a project status indicator.

A blue NeoPixel status means the sketch is currently accessing the Internet, either connecting to the WiFi hotspot or accessing Adafruit.io to grab the date and time.

A green NeoPixel status means the sketch is currently updating the display for the specified month and will turn off when it is completed. This can take a few seconds since ePaper displays are not very speedy at refreshing their screens.

A red NeoPixel status means there is a network communication issue. Pressing the buttons will have no effect if the NeoPixel is showing one of these status colors. Wait for the NeoPixel to turn off before pressing one of the buttons to change the month display.