Regarding ladymcdonald's comment about June 21 always being the first day of summer prior to the last 5-10years... When I took Geology in college in the late 1960s is when I learned about the astronomical dates for the equinoxes and how the seasons' first dates fluctuated. So, the first day of summer was not always listed as June 21 as early as the late 1960s. Of course, the first day of summer has always fluctuated (including prior to late 1960s,) but people were probably like me... uniformed of factual information.
Regarding ladymcdonald's comment about June 21 always being the first day of summer prior to the last 5-10years... When I took Geology in college in the late 1960s is when I learned about the astronomical dates for the equinoxes and how the seasons' first dates fluctuated. So, the first day of summer was not always listed as June 21 as early as the late 1960s. Of course, the first day of summer has always fluctuated (including prior to late 1960s,) but people were probably like me... uniformed of factual information.