Geochronous clock
Geochronous clock
The earth map moves almost imperceptibly from left to right, synchronized with the earth's rotation, from west to east, while the time scale at the top is still. The upper scale shows summer time, the lower part of the scale shows winter time. Between the vertical black lines on the right and left, the earth is shown for a period of 24 hours. It is morning on the left half and afternoon on the right half. The time zones are marked with letters. Vertical above the black point near the center of the clock you have to think of the current position of the sun. Due to the different orbital speed of the earth around the sun and the inclination of the earth's axis, this point moves in relation to the center of the earth around the sun during a year apparently on an eight (analemma) In the illuminated part of the map it is day, in the dark part it night. The left edge of the light zone represents the sunrise, the right edge represents the sunset. If you imagine a horizontal line through a place, you can read off the times for sunrise and sunset on the time scale.
Time zones
A time zone is formed by those parts of the earth's surface in which the same, state-regulated time and date, i.e. the same zone time, apply. In directly adjacent time zones, the time is usually one hour back (west) or ahead (east).
Starting from the zero degree of longitude through Greenwich (London), the time zone theoretically changes at every 15th degree of longitude by one hour (360 degrees of longitude divided by 24 hours). Usually, however, the zones are adapted to the national borders.
12 hours less to the west and 12 hours more to the east require a date line. It meanders through the Pacific to avoid mainland. One consequence is that there are two different days of the week on earth 23 hours a day. There is only a day of the week on Earth between 1 p.m. and 2 p.m. CET.
Image source: CC license Wikipedia
