In Neopaganism
In some Neopagan religions, a "Celtic calendar" loosely based on that of Medieval Ireland is observed for purposes of ritual. Adherents of Reconstructionist traditions may celebrate the four Gaelic festivals of Samhain, Imbolc, Beltane and Lughnasadh.
Some eclectic Neopagans, such as Wiccans, combine the Gaelic fire festivals with solstices and equinox celebrations derived from non-Celtic cultures to produce the modern, Wiccan Wheel of the Year. Some eclectic Neopagans are also influenced by Robert Graves's fictional "Celtic Tree Calendar", which has no foundation in historical calendars or actual ancient Celtic Astrology.
Read more about this topic: Celtic Calendar