If the author wants to be absolutely exact he needs to tell us what December 25 he is talking about: the old, the middle, or the new December 25th.
>> “There is no mention in this article about the adoption of the Julian calendar or the later change to the Gregorian calendar.” <<
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Those are the foolish works of men.
Yehova’s days are from sunset to sunset, and his years begin with the new moon that comes at the time of the Aviv barley.
This is obviously not a date that can be fixed in advance, and must be observed on his holy mount Moriyah in Jerusalem each year.
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If December 25th was accepted as the birthday of Christ in the Julian Calendar why not celebrate it on that day after 1582? The Gregorian calendar omitted ten days to compensate for the miscalculated (by minutes) solar year and return the seasons (equinoxes and solstices) to better harmonize with New Years Day. Regardless, If they accepted and celebrated December 25 we can too (though folks alive then would have thought of that day as Dec 15)
“There is no mention in this article about the adoption of the Julian calendar or the later change to the Gregorian calendar.”
It’s irrelevant actually. Because the Julian calendar was introduced in 46 BC. Since the Julian calendar is only .002% off per year compared to its Gregorian replacement, in Anno Domini when Jesus was born, the difference was about 8 hours compared to the Gregorian calendar, if that calendar was used in its place.