Calendar Seasons

Source: http://www.kmvt.com/content/news/Weather-Blog-Welcome-to-fall-Wait-what-323791871.html

Had a discussion with the 6 year old about seasons recently. Turns out, seasons in the USA don't start on the first of the month, they start on the 21 or 22nd of the month.
Winter - Winter Solstice - Dec 22nd
Spring - Spring Equinox - March 20th
Summer - Summer Solstice - June 21st
Autumn - Fall Equinox - September 23rd
Which is still around three months per season, but sort of more in line with the hours of sunlight, I think, rather than a date on the calendar. Further research indicates that maybe the reason is that this is the astronomical seasons, whereas the first of the month is what is used when recording data, as the 1st of the month is at the same time, but Solstice etc might not be on the same day every year.