December the 25th is not a "Winter Holiday", it is designated as Christmas Day.
It is also very likely NOT the birthday of Jesus the Christ, but it is a designated day to remember that event. (Shepherds would not likely have been "in the field" in winter.) The event was attended by some celestial signs and visitors, but nobody bothered to mention the actual date. Perhaps the date was considered of less significance than the import of the event. God had visited man - no, God had become a man. The second Adam had been born to redeem us all from the taint left by the first Adam. Good News, indeed.
Here is the major distinction of Christianity from other religions: The way of salvation was invested not in following elaborate rules, but in a Person. Messiah Jesus came not to condemn the world, but to save it. In those hours on the cross, He absorbed all the sins of the world - past, present, and future.
And that is why I can wish you a very Merry Christmas.