My solution. Slightly different results but I'm wondering if I picked the wrong day as first of winter which of course would change spring/fall. Might be good to add first day of winter to the challenge to get results more in line.
I've matched output here by accident genuinely without intending to. I was kind of annoyed at the lack of an end date for seasons so I just did the two ranges we had and then 'else Fall', completely disregarding the fact a fourth season exists to see if I could work out the change later. Not sure why it would be set up that way though.