Short answers, pulled from the story.
The Floralia festival took place from the 27th of April to the 3rd of May. Ovid described hares and goats being released while crowds were pelted with vetches, beans, and lupins.
Walpurgis Night commemorated the official canonization of Saint Walpurga on the 1st of May 870. Folklorist Jack Santino noted that her day and its traditions are traceable to pre-Christian celebrations.
Special bonfires were kindled whose flames had protective powers for people walking around or between them. All household fires were doused then re-lit from the Bealtaine bonfire.
Pope Pius XII chose this date in 1955 as a counterpoint to communist International Workers Day celebrations. The 1st of May is one of two feast days dedicated to the Catholic patron saint of workers.
The first Lei Day was celebrated on the 1st of May 1927 in Honolulu. Leonard Red and Ruth Hawk composed the song May Day Is Lei Day in Hawai'i.