Picky, picky . . . whenever the change happens from one season to the next, there is the actual day on which it occurs and the 'first day of the new season'. Take for example that the March equinox in 2021 happened in the Northern Hemisphere on Saturday, March 20, at 5:37 A.M. EDT. Yes - but therein lies the difference because (to many) the first day of Spring (in this case) is the first full 24-hour day following . . . ie. TODAY!!! No matter how you look at, I doubt there has ever been a more welcome Spring than we share this year.
As it was a lovely warm afternoon here in Southern England and such a nice thread by Margot, I thought I would post a couple of photos from my garden today, 'Happy first day of Spring'. Only the very early starts, but they are there. Magnolia White star and Handkerchief tree Davidia involucrata. The latter will not produce the tell tell white bracts for another 3 years.
This is in the same vein as the original posting, a "Mutts" cartoon: March 21 2021, Sunday Comic Strip (mutts.com)