Winter solstice instant of the solstice can be calculated, direct observation of the solstice by amateurs is impossible because the sun moves too slowly or appears to stand still (the meaning of "solstice"). However, by use of astronomical data tracking, the precise timing of its occurrence is now public knowledge. One cannot directly detect the precise instant of the solstice (by definition, one cannot observe that an object has stopped moving until one later observes that it has not moved further from the preceding spot, or that it has moved in the opposite direction). Further, to be precise to a single day,
Labours of the Months Ice Age has been detected in differences between early and late examples. Most sculptured cycles in Europe, especially when compressed into the archivolt of a portal, consist of an astrological symbol beside, above or incorporated in a sculpture or relief illustrating a monthly labour. A few sculpted examples of the many surviving are: The Labours of the months often occur in those rose windows that are dedicated to the Creation, the circular nature of the window suiting the cyclic theme. In these windows, the months are part of a complex iconographical scheme. Other windows have the Labours of the Months