Sources and image credits

Autumn equinox on 23 September: why autumn in the Netherlands has two start dates

Source

KNMI – KNMI – Autumn
U.S. Naval Observatory – https://aa.usno.navy.mil/api/seasons?year=2026
Hart van Nederland – Astronomical autumn begins: warm and dry weather continues | Hart van Nederland
Met Office (UK) – Understanding equinoxes and solstices – Met Office
U.S. Naval Observatory – https://aa.usno.navy.mil/api/rstt/oneday?date=2026-09-23&coords=52.10,5.18&tz=2
U.S. Naval Observatory – https://aa.usno.navy.mil/api/rstt/oneday?date=2026-09-26&coords=52.10,5.18&tz=2
MeteoSwiss (Swiss weather service) – Calendar, astronomical and meteorological seasons – MeteoSwiss
NOAA National Centers for Environmental Information – Meteorological Versus Astronomical Seasons | News | National Centers for Environmental Information (NCEI)
aa.usno.navy.mil — Used for: Source reference for this article
aa.usno.navy.mil — Used for: Source reference for this article

Image credits

The Markermeer on a grey, windless day in early October 2014: flat water, a low islet with trees, a buoy and a long, low horizon.Linus Follert · CC BY-SA 2.0 · Original source

The 1919 sundial at De Eshof cemetery in Haren, photographed on 22 September 2010, around the start of the astronomical autumn.Wutsje / Wikimedia Commons / CC-BY-SA 3.0 · CC BY-SA 3.0 · Original source

The earth seen from a geostationary satellite around the September equinox of 2010, at about six o’clock in the morning local time. The boundary between day and night then runs almost straight from north to south. Image by NASA Earth Observatory with data from EUMETSAT.NASA Goddard Space Flight Center from Greenbelt, MD, USA · Public domain · Original source