Christmas: Roman Catholic Church settled on December 25 as the birthday of Jesus to tie his birth to the winter solstice and Saturnalia, a festival dedicated to the Roman deity Saturn. By choosing December 25, as Jesus' birthday, the church could co-opt the popular pagan festival, as well as the winter celebrations of other pagan religions.
Some religious researchers pinpoint the birth of Jesus of Nazareth to have occurred between 6 B.C. and 4 B.C., based on the biblical story of Herod the Great. This date of Jesus’ birth was further established by correlating to the "Star of Bethlehem," which appeared as a comet in the eastern skies. This phenomenon occurred on 17th June 2 B.C. Also, according to the Holy Quran Jesus was born in summer when the date palms shed their fruit.
Easter (or the festival of Ishtar): Festival of Ishtar was celebrated every year in spring in Assyria and Babylon in the name of the goddess of fertility and sex. Her symbols Eggs and Bunny are sex symbols. Constantine in Christianizing Europe changed the commemoration of Easter to represent the resurrection of Christ.
The above two examples should indicate to a thinking mind how religious events and rituals are misplaced over the years and have little relevance to the reality.