It’s hard to know when the last cool day of Spring happens.  You don’t really notice it until it’s come and gone.  It’s easier to notice the first cool day of Fall.  Yesterday, for me at least, was that first cool day.  I was sitting in my office reading, and I realized I was chilly.  Not pleasantly cool, but actually chilly.  This isn’t really a problem for a knitter.  I went to the sock basket (abandoned since some time in May) and pulled out something warm and woolly.  They totally took care of the problem.  It feels like a milestone somehow, a marker in my personal calendar of the year, and a more significant one than any particular date.