How do I set the time and day on my TH6220D thermostat?

Press the SET CLOCK/DAY/SCHEDULE button, then press the up or down arrow to set the clock time. Next, press the SET DAY button and use the arrows to select the current day of the week. Finally, press DONE to save your settings and exit. If the display flashes 'Set Clock', the thermostat will follow your weekday settings until you reset the time and day correctly.