The BBC News magazine looks at the question of
when spring actually starts:
"You would not regard the first three weeks of June as spring, yet historically summer does not start until 21 June," says a spokesman for the Met Office. "Equally, the bulk of people now regard 1 March as the first day of spring."
Historically spring starts on the day of the vernal equinox, which usually occurs on the night of 20/21 March.
After all, summer is commonly decreed to start on 21 June - the Summer Solstice - yet the following day is known as MID-summer's day.
I've always thought that spring would run, in the northern hemisphere, from the start of March to the end of May, regardless of what the actual weather was like. Though perhaps that has to do with having grown up in Australia, in the Southern Hemisphere, where there are fewer ancient date-keeping traditions and things are somewhat simplified (for example, the Australian financial year starts on the first of July, and the Australian school/university year runs from the end of January to the end of November, give or take a few weeks, while in the northern hemisphere, the financial year starts/ends in early April (which, apparently, comes from ancient Roman tax laws or something), and the school year starts in September (as per the Field Mice song and the gripes about AOL dumping its naïve users on an unsuspecting Usenet). Similarly, the seasons are held to align evenly with 3-month boundaries, even though the start of a season usually feels more like the preceding season. I wonder how long ago this 3-month system replaced the traditional definitions of the seasons.