Why does my thermostat read differently from a thermometer?

Honeywell digital thermostats are designed to display the room temperature in a way similar to how people sense temperature. This means the thermostat takes into account not just the ambient air temperature but also the radiant temperature of objects in the room (i.e., wall and furniture). Room thermometers often only read ambient air temperature so they will not match the thermostat reading. Also, Honeywell thermostats do round in the display to the nearest whole number (half number in Celsius) and to the temperature setting. For example, if you have the thermostat set to 72 degrees the system will turn on and off but the inside reading on the thermostat never changes from 72. The actual temperature did fall to 71 or up to 73 and that is what turned on the heating or cooling but the thermostat display will stay at 72 to avoid jumping up and down constantly.