This display shows the seven days of the week.
Seven days are sometimes indicated on a circle with a hand in its center pointing to the day. This device can easily be spotted under the dial by its 7-tooth star which corresponds to the seven days of the week. The days of the week can also sometimes be arranged on a retrograde display.
Another way of displaying the day is on a disc that is placed behind the aperture. The day is sometimes written in two letters, three letters or in full. Also, some companies can deliver their watches with the day in the specific language of the place where they will be sold.