Last spring, we had 3 nights of frost at the end of March after a run of beautiful, sunny, 80-degree days. It was cruel and unusual and I really should use that as a benchmark for putting sensitive plants in the ground outside even though most years, plants have been out there for 5-6 weeks by then, just fine.
I think the Vernal equinox is a fine, worthy thing to celebrate, so March 20 is a great milestone for that reason, even if spring might technically refuse to arrive in full everywhere that day. The signal has been given, for all long-day plants to bloom as soon as they grow enough to do so. The angle (and power) of the sun will begin to change dramatically.
(Who else remembers the Bartles'n'James commercial celebrating the vernal equinox?)
Pirl, that's so cool!
Bob, thanks for sharing this fun toy!