"May Day festivals, which began with great public gaiety, usually ended in orgiastic displays of sexual licentiousness. Marriage vows were temporarily forgotten during this honey month. People coupled freely in the woods and fields, fertilizing the soil and each other, sharing a fervent participation in the regenerative magic of the earth."
A German-born lady told me how women of all ages would stand at their doorways, dolled up, waiting... Any resulting babies were deemed legitimate.
As for Holi in India (celebrated in their - earlier - Spring), here is the past, imagined by someone with a deep knowledge of the country and its people: