Today is the Spring Equinox, traditionally The First Day of Spring.
But it's not.
Today is the exact middle of spring. Similarly, the Summer Solstice is the middle of summer (from there, the days get shorter until the Winter Solstice).
There are 4 seasons, each 91 days long, with 45 days between a Solstice or Equinox. So, the real start of each season is (approximately) as follows:
|Spring||February 2 (45 days before the Equinox)|
"Search your heart, Luke. You know it to be true."