People before globalization worked with the seasons, the sun the equinoxes etc. Easter is Ostara celebrating the spring equinox - Ostara is a Goddess that lives in the moon with her hate and came to earth to visit children and to entertain the children she turned a chicken into a hare and it laid coloured eggs.
The new year 1st Jan is the man made one.
The feast on the 25th is to celebrate the days getting longer again. The Druids measured the day lengths. The shortest day in the Northern hemisphere is the 21st/22nd. 4-5 days later there would be a feast celebrating the confirmation that the sun was not dieing and was coming back.
There are many calender celebrations around the world because it was very important to life to keep touch with your actual environment.
