- May Day which has its traditional origins in the Celtic holiday of Beltane and the Germanic holiday of Walpurgis Night.
- International Workers' Day [aka Labo(u)r Day] which has its origins in Chicago's Haymarket Affair. [Chicago Historical Society's Haymarket Affair Digital Collection]. Ironically, while the International Workers movement chose May 1 to honor the Haymarket Affair, Labor Day is observed in September in both the U.S. and Canada.
- Loyalty Day - a holiday created in America in the 1950s to 'counter-balance' International Worker's Day.
- MayDay - "An initiative to protect cultural heritage from disasters."
Note: the distress call "Mayday!" actually derives from the French words venez m'aider - meaning "come help me."