Today ( 22nd September ) marks the occasion of the Autumnal Equinox within the Astronomical calendar. This means that our night and day are of approximate equal length as the Equator passes the centre of the Sun. Our North and South poles are not tilted towards or away from the Sun, as on other occasions, but are aligned to , theoretically at least, the same amount of daylight to both of Earth's hemispheres.
The next notable occasion is that of the "winter solstice" on the 21/22 nd December, with the 21st being the shortest day of the year in the context of daylight.
The Meteorological Calendar is derived from the Grigorian Calendar which we assiduously follow . The seasons are simply split into three monthly blocks, which makes forecasting and the comparison of statistics easier to follow. These are straightforward.....Spring is March to May inclusive, Summer is June to August, Autumn is September to November and Winter is December through to February.
And , if you really want to be precise, we now have 100 days left to the end of the year!!!