For 2023 the Winter Solstice in on 21 December, as is often the case. Here is HP Blavatsky on this ancient sacred time:
"We are in the Winter Solstice, the period at which the Sun entering the sign of Capricornus has already, since December 21st, ceased to advance in the Southern Hemisphere, and, cancer or crablike, begins to move back. It is at this particular time that, every year, he is born, and December 25th was the day of the birth of the Sun for those who inhabited the Northern Hemisphere. It is also on December the 25th, Christmas, the day with the Christians on which the “Saviour of the World” was born, that were born, ages before him, the Persian Mithra, the Egyptian Osiris, the Greek Bacchus, the Phoenician Adonis, the Phrygian Attis. And, while at Memphis the people were shown the image of the god Day, taken out of his cradle, the Romans marked December 25th in their calendar as the day natalis solis invicti. [Birth of the Invincible Sun]
Sad derision of human destiny. So many Saviours of the world born unto it, so much and so often propitiated, and yet the world is as miserable—nay, far more wretched now than ever before—as though none of these had ever been born!"