A pair of twin sisters, the elder sister was born before the younger sister, and the younger sister. Why?

When my mother gave birth to two sisters, she crossed the international international date line from west to east. My sister was born earlier than my sister in time, but my sister was born after international date line, so the date should be reduced by one day, that is, the day after. Judging from the date, my sister was born earlier than my sister.

The earth is a planet in the solar system. It revolves around the sun and rotates once a day. Therefore, the half sphere of the earth illuminated by sunlight forms the day, while the other half sphere facing away from the sun is the night, and the transition area between them is morning and dusk. The earth keeps turning from west to east, and the morning, day, faint and night on the earth also keep turning from east to west, appearing in various places repeatedly.

All parts of the world take the position of the sun they see as the standard for determining a day, and take a meridian corresponding to their position on the other side of the earth as the "international international date line", also known as the international international date line. In this way, there are many "international international date line", which is very inconvenient to use. In order to solve this problem, we should stipulate an "international international date line" which is the same and comparable all over the world.

With the establishment of the standard time and time zone system, the twelve time zones in the east and west overlap, with the same time and different dates. In order to avoid confusion, Meridian 180 is recognized as an international international date line, because it is an international international date line based on Greenwich Mean Time. This "International international date line" is called "International international date line".