Wheel of the Year
(needs more work)
For many thousands of years humans seem to have divided the year into eight parts.
They begin with the coming of the Winter Solstice.
December 21 to 23 Winter Solstice, Christmas
February 2 (Candlemas, Imbolc, Groundhog Day)
March 21 (about) Spring Equinox, Ostare, Eostre (Easter)
May 1 May Day, Beltane, May Eve, Samradh, Cetsamain, Walpurgis Night.
June 21 (about) Summer Solstice, Midsummer, Saint Johns day festival
August 1
September 21 (about)
October 31 Halloween, Samhain, Allantide, All Hallows Eve
Even most major Christian festivals fall on or very close to these days.