A watch may include a first display unit, a second display unit, a first polarizer set, and a second polarizer set. The second display unit may be positioned over the first display unit and may transmit light. One of the first display unit and the second display unit may display a time information image that indicates time. The other of the first display unit and the second display unit may display non-time information image, e.g., a user interface element. The first polarizer set may be positioned between the first display unit and the second display unit. The second polarizer set may be positioned on the second display unit. One of the first polarizer set and the second polarizer set may rotate relative to the other for enabling the watch to conceal or show the time information image.