Most people know without a doubt that the First Day of Spring won't arrive until March 20. That's because it's tradition. And their calendars say so. But they're wrong, too. That won't be the First Day of Spring either.
March 20 will be, instead, the first day of what is known as Astronomical Spring. That's because March 20 is the day of the Vernal Equinox, and the Astronomical seasons are determined by the tilt of the earth's axis. So March 20 will be the first day of Astronomical Spring. But Astronomical Spring is not the first Spring of the year.
Those people trying to tell you that today is the First Day of Spring think they've really pulled a fast one on you. That's because they've discovered what is called Meteorological Spring. Meteorological Spring is based on temperature rather than on what the earth's axis is doing. The three coldest months--December, January, and February--are Meteorological Winter. So, guess what, March, April, and May make up Meteorological Spring. So March 1 is the first day of Meteorological Spring!
But if they had read further in Wikipedia, like I did, they would realize that Meteorological Spring is still not the first Spring of the year.
Here's where it gets good. There's a third way of classifying the seasons. These are the Solar Seasons. Solar Seasons are determined not by the tilt of the earth's axis, or the temperature, but by the amount of sunlight the earth receives. Solar Winter consists of the three months that receive the least sunlight: November, December, and January. Therefore Solar Spring--the official First Spring of the Year--begins on February 1.
I think you've heard me say or seen me write that I have always considered February to be the first month of Spring. All this time I thought I was just being ironic, and it turns out I was right.
So when is the actual First Day of Spring? It doesn't matter. We missed it.