Today is the beginning of autumn 2025 and why are there two dates?

"January, February, March, April, the clock never stands still," goes Rolf Zuckowski's children's song. While the lyrics help with learning the months of a year, the catchy tune doesn't reveal when the four seasons begin. Admittedly, not all seasons begin the same.

Read more after the ad

Depending on whether the periods of the year are viewed astronomically, and thus calendar-wise, or from a meteorological perspective, the beginning and end of spring, summer, autumn, and winter result in different dates, some of which even vary slightly from year to year. So, no offense to Rolf Zuckowski; we'll explain using autumn as an example:

The meteorological start of autumn, also called the climatological start of autumn, is easy to remember. It always falls on the first day of the month in which the equinox occurs, which is in September every year. From a meteorological perspective, autumn therefore always begins on September 1st.

Read more after the ad

There is a simple and practical reason for this: the meteorological definition is intended to give all four seasons a constant length in order to enable uniform climate and weather records and to simplify comparisons over long periods of time.

In Germany and the entire northern hemisphere, however, autumn doesn't begin until September 22nd this year. For those who want to know exactly: at 8:19 p.m. Central European Time (CEST).

This has to do with the so-called autumnal equinox and the north-south movement of the sun. The date of the beginning of calendar autumn, also called the beginning of astronomical autumn, varies from year to year and falls on different dates in September.

The equinox (also known as day and night) refers to the two calendar days of the year on which day and night are approximately equal in length. So far, so obvious. In September, the sun moves across the equator to the Southern Hemisphere, ushering in spring there, while autumn begins in the other half of the Earth.

Read more after the ad

In half a year, the sun will cross the equator again, return to the Northern Hemisphere, and bring spring to the north and autumn to the south. And then? The whole thing starts all over again. Just like with Rolf Zuckowski.

Every child knows that autumn is followed by winter—but when exactly? Here, too, there are two different dates. Calendar autumn ends on the shortest day of the year. This occurs when the sun reaches its lowest point in the Northern Hemisphere. Winter is here. This year, the beginning of calendar winter in the Northern Hemisphere is on December 22nd at 4:02 p.m. Central European Time.

Meteorology, however, continues to follow its own system when dating the beginning of winter. The end of autumn and the beginning of winter are determined by the so-called winter solstice. From a meteorological perspective, autumn ends on November 30th, while winter begins on December 1st.

Full moon over Aachen on January 13, 2025.

Read more after the ad