If you are searching, then you are at the right place. Around 150 AD Christian churches chose to take over the pagan holiday of Saturnalia (the winter solstice) and observe 25th December as Christ's birthday. Later, when the cult of the Virgin Mary became popular, it was believed that the Christian era should begin on the day of the conception of Christ, that's, 9 months previously on 25th March, which they named Ladyday. The year finished on the following 24 th and started on 25 th. Here is available .
All moveable feasts in the church calendar relate to . In turn, gospel tradition associated Easter to the Jewish festival of Passover, which in turn was related to the spring equinox, the phase of the moon and the celebration of the Sabbath. Over the centuries, by following the Julian. the Easter holiday was moving away from the spring equinox towards the summer solstice. The new system embraced in the 16th century by Pope Gregory, defined a calendar with a year length of 365 days, 5 hours, 40 minutes, 20 seconds. Therefore every 400 years 3 days needed to be dropped. If they were divisible by 400, so those years that were divisible by 100 would only be leap years. Pope Gregory declared that Thursday 4 th October 1582 in the Julian
should be immediately followed by Friday 15th October in the Gregorian to correct errors which had built up over cent.