Haven't looked at that vid, (not enough hours in the day ...) But this year today, 21 Dec. is indeed the Winter Solstice in the Northern hemisphere. Irrespective of latitude.
The exact date varies according to the Gregorian calendar, 365 days/year, but 366 every fourth (leap) year. Rather than the actual 365.242199 days or so that it takes the Earth to orbit the sun.
December Solstice: the Shortest (and Longest) Day
The December solstice can be on December 20, 21, 22, or 23.
December 21 or 22 solstices happen more often than December 20 and 23 solstices. The last December 23 solstice was in 1903 and the next one is in 2303. A December 20 solstice is also rare, with the next one in the year 2080.
As to the timing of sunrise and sunset, that is subject to the movements of the Equation of Time, largely because the Earth's orbit is slightly elliptical rather than circular:
Equation of Time
FWIW, Today at my location I have 7hrs 56'12'' of daylight. Yesterday was six seconds longer. Tomorrow will be one second longer. June 21 (Summer Solstice) will be the longest day. 16 hrs 31 minutes 13 seconds.
FWIW 6 June 1944 was not actually "the longest day". But near enough.