Really, it DOES matter. Does YHWH change? Did YHWH ordain His Holy Days? And what is the purpose of those days?
It matters because those TRUE Holy Days, and their purpose, go wanting. I doubt that more than 1 in 100 Christians even know what they are.
Last thing we want as Christians is for the pagans or their successors to get the idea they can whipsaw us around and make us do things.
LOL! They already have.
You are confounding a calendar with a religious rite. The solstice is a phenomenon that happens with or without religion ~