in the early church, they believed that a prophet should die on the same day that he was conceived. the early church had jesus' death as occurring on the 25th of march, add 9 months, and we get to december 25th. christians were doing their own calculations, irrespective of the pagans and pagan traditions. in pagan societies there were multiple deities, gods and goddesses, and they would have many festivals and celebrations for them throughout the entire year. in ancient rome for example there was not one month of the year free of these festivals (feriae), so it would be almost impossible for christians to choose a date that didn't coincide with one of the many pagan festivals. our beautiful and peaceful christian celebrations developed in christendom were and are very different from the many pagan celebrations, the ancient roman scholar varro defined these pagan festivals as "days instituted for the sex of the gods." the early church calculations concluding december 25th as the date to celebrate jesus' birth ironically was one of the few dates that didn't have pagan celebrations on it, but even if there had been an overlap it would be irrelevant to christians, and it certainly would not be "stealing" any pagan festival.
Poland