Can I switch between 2 and 4 period programming?

To change the # of periods per day – 2 vs. 4:

1. Take the front cover off the stat off the wall. 
2. Look on the circuit board to find the dip switch table which tells you what the dip switches are for.

The dip switches are the very small white protrusions on the top of the grey vertical box just the right of the table.

There are a total of 8 dip switches labeled 1 thru 8.  The number text is small and difficult to see.

        3. Move dip switch #3  (the 3rd one from the bottom) to the opposite position carefully with a fine-point pen, toothpick, or similar. 

Right = 4

Left = 2

        4. Now press the small black button on the circuit board on the left labeled “HW RSRT” to read the new setting.  

There are 2 buttons, hit “HW RST” only.  (If you press SW RST, it will change your program back to the factory defaults).

        5. Finally, put the front half of the thermostat back onto the wall.