Comment by Humphrey

Oh, I have never heard of seasons starting mid-month. My mind is blown!

In Australia it's just split up by months, with each season being 3 months long:

March 1 - Autumn starts June 1 - Winter starts Sept 1 - Spring starts Dec 1 - Summer starts

Of cause, those in far northern Australia, only really have Dry and Wet seasons. I have no idea when those are.