A clock takes the form of a translucent globe (10) mounted over a base (20) marked circumferentially with indicia (26) which denote the hours of the day. The current time is indicated by a pointer (16) which circles the base once in (24) hours. The globe rotates at the same speed and is lit from within by a light source which is shaded to throw a night time shadow (80) and give the globe, with its surface markings (82), the appearance of the planet earth illuminated by the sun. The shadow moves according to the time of day and the season of the year, to show the current solar illumination of the earth. A calendar display may also provided on the base.