This list does not include every pagan event or festival, but encompasses some of the more common ones celebrated by pagans around the world. It also includes holidays from Celtic, Germanic, Roman, Afro-Caribbean, Shinto, and folk cultures. There are a large number of folk witches and pagans who observe specific Catholic saint feast days, so I've included some of those as well.
OCTOBER
October 4
Feast Day of St. Francis of Assisi
Feast Day of Orula
October 31
Samhain Eve
NOVEMBER
November 1
Samhain
All Saint's Day
November 5
Guy Fawkes Night
November 11
Martinmas (Old Halloween)
December 4
Feast Day of St. Barbara
Feast Day of Chango
December 17-23
Saturnalia
Winter Solstice
Yule (begins)
December 31
Hogmany
Omisoka
JANUARY
January 1
New Year's Day
January 5
Yule ends
FEBRUARY
February 1
Imbolc
February 2
Feast Day of Oya
February 3
Setsubun
February 14
Lupercalia
Feast of St. Valentine
MARCH
March 3
Hina Matsuri
Ostara
Shubun-sai
March 22
Feast Day of Orisha Oko
APRIL
April 22
Earth Day
April 30
Walpurgis Night
MAY
May 1
Beltane
May Day
May 5
Koi-no-bori
JUNE
June 6
Feast Day of Ochosi
Summer Solstice
Litha
June 24
St. John the Baptist Day
June 29
Feast Day of Ogun
June 30
Nagoshi-no-Oharai
July 13-15
Oban Festival
July 31
Lammas Eve
AUGUST
August 1
Lammas
Lughnasadh
SEPTEMBER
September 7
Feast Day of Yemaya
September 8
Feast Day of Oshun
Fall Equinox
Mabon
Harvest Home
September 24
Feast Day of Our Lady of Mercy
Feast Day of Obatala
September 27
Feast Day of Ibeji
September 29
Feast Day of Erinle