As to the on-or-before-Christmas vs “Christmastime”, the proverbial twelve days of Christmas are the twelve days after Christmas, ending with The Epiphany, the feast of the Magi, on January 6. The days before Christmas are Advent, the days of preparing for the birth of Jesus.
Thank you for pointing that out. You beat me!
Now days Christmas ends on the first day of Christmas— of the old Christian Christmas.
Christmas always used to begin, universally, on Christmas Eve decorating the tree, the season of Christmas began on Christmas Day, lasting for The Twelve Days of Christmas.
As you said, truly, Christian Christmas feast days were adhered to by all.
I need to research when and why the modernist cultural shift changed out even the memory of all that Christmas tradition. Wiped out, generally, today.