Beltane When to Celebrate

By Celtic reckoning, the actual Beltane celebration begins on sundown of the preceding day, April 30, because the Celts always figured their days from sundown to sundown. And sundown was the proper time for Druids to kindle the great Belfires on the tops of the nearest beacon hill (such as Tara Hill, Co. Meath, in Ireland). These “need-fires” had healing properties.
Frequently, cattle would be driven between two such bonfires (oak wood was the favorite fuel for them) and, on the morrow, they would be taken to their summer pastures. More about Beltane here.