The Christmas Season.
He appears to Scrooge on Christmas Eve, but the time period of Christmas Yet to Come is unspecified.
advent is the 4-week period prior to Christmas, with Christmas as the pinnacle and ending of the Advent.
The period of Christmas is referred to as "The Yuletide". This harks back to pagan celebrations at the Winter Solstice. I think some of Scandinavians say "God Jul" (or something like that) for "Merry Christmas".
Both.
Christmas fair on a frozen River Thames
Advent
Christmas
The Saturday night Live Christmas song is about it soon being Christmas. It is also about quashing negative views of Christmas and the singers emphasising their excitement about the festive period.
The time before Christmas is referred to as Advent. Some churches observe this beginnining four Sundays before Christmas Day.
Christmas Fair on a frozen River Thames (known as a Frost Fair)
Variable, depending on the owner.