 For example, they commonly allow setting temperatures for two, four, or six periods each day, and rather than being limited to a single "hotter" temperature and a single "colder" temperature, digital thermostats usually allow each period to be set to a unique temperature.The periods are commonly labeled "Morning", "Day", "Evening", and "Night", although nothing constrains the time intervals involved.Digital thermostats usually allow the user to override the programmed temperature for the period, automatically resuming programmed temperatures when the next period begins.