The ancient Celts defined seasons based on the solar cross-quarter days (the midpoints between solstices and equinoxes):
This is why, in Ireland, February 1 is often considered the first official day of spring, and November 1 the first day of winter. when do the four seasons start and end
| Season | Astronomical Start (approx.) | Astronomical End (approx.) | Meteorological Start | Meteorological End | | :--- | :--- | :--- | :--- | :--- | | Spring | March 20 | June 20 | March 1 | May 31 | | Summer | June 20 | September 22 | June 1 | August 31 | | Autumn | September 22 | December 21 | September 1 | November 30 | | Winter | December 21 | March 20 | December 1 | February 28/29 | The ancient Celts defined seasons based on the
| Season | Astronomical Start | Astronomical End | Meteorological | |------------|--------------------------|--------------------------|----------------| | Spring | Mar 20–21 (Equinox) | Jun 20–21 (Solstice) | Mar 1 – May 31 | | Summer | Jun 20–21 (Solstice) | Sep 22–23 (Equinox) | Jun 1 – Aug 31 | | Autumn | Sep 22–23 (Equinox) | Dec 21–22 (Solstice) | Sep 1 – Nov 30 | | Winter | Dec 21–22 (Solstice) | Mar 20–21 (Equinox) | Dec 1 – Feb 28/29 | This is why, in Ireland, February 1 is
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To complicate matters further, different cultures around the world define seasons in their own unique ways.