These are the most familiar dates in calendars. They are defined by the solstices (longest/shortest days) and equinoxes (equal day/night). Dates vary by ±1 day due to leap years and Earth’s elliptical orbit.
| Season | Start Event | Typical Start Date | End Date | |--------|-------------|--------------------|----------| | | Vernal Equinox | September 22–23 | December 21–22 | | Summer | Summer Solstice | December 21–22 | March 19–21 | | Autumn | Autumnal Equinox | March 19–21 | June 20–21 | | Winter | Winter Solstice | June 20–21 | September 22–23 | when the seasons start and end
| Season | Start Event | Typical Start Date | End Date | |--------|-------------|--------------------|----------| | | Vernal Equinox | March 19–21 | June 20–21 | | Summer | Summer Solstice | June 20–21 | September 22–23 | | Autumn (Fall) | Autumnal Equinox | September 22–23 | December 21–22 | | Winter | Winter Solstice | December 21–22 | March 19–21 | These are the most familiar dates in calendars
