May is the fifth month of the year in the Julian and Gregorian calendars and the third of seven months to have a length of 31 days.
May is a month of spring in the Northern Hemisphere and autumn in the Southern Hemisphere. Therefore, May in the Southern Hemisphere is the seasonal equivalent of November in the Northern Hemisphere and vice versa. Late May typically marks the start of the summer vacation season in the United States (Memorial Day) and Canada (Victoria Day) that ends on Labor Day, the first Monday of September.
No other month either begins or ends on the same day of the week as May in any year. This month is the only month with these two properties. May, however, starts and ends on the same day of the week as January of the following year. Also, in common years, May begins and ends on the same day of the week as August of the previous year, and, in leap years, it begins on the same day as February, March, and November of the previous year. In years immediately before common years, May begins and ends on the same day of the week as October of the following year and ends on the same day of the week as February of the following year. In years immediately before leap years, it begins and ends on the same day of the week as January and July of the following year and begins on the same day of the week as January, April, and July of the following year. 
May (in Latin, Maius) was named for the Greek GoddessMaia, who was identified with the Roman eragoddess of fertility, Bona Dea, whose festival was held in May. Conversely, the Roman poet Ovid provides a second etymology, in which he says that the month of May is named for the maiores, Latin for "elders," and that the following month (June) is named for the iuniores, or "young people" (Fasti VI.88).
Mayapples blooming. Common name given due to the plant's tendency to bloom in the month of May.
Mayovka, in the context of the late Russian Empire, was a picnic in the countryside or in a park in the early days of May, hence the name. Eventually, "mayovka" (specifically, "proletarian mayovka") came to mean an illegal celebration of May 1 by revolutionary public, typically presented as an innocent picnic.
Eta Aquariids meteor shower appears in May. It is visible from about April 21 to about May 20 each year with peak activity on or around May 6. The Arietids shower from May 22 - July 2, and peaks on June 7. The Virginids also shower at various dates in May.
The May birth flowers are the Lily of the Valley and the Crataegus monogyna. Both are native throughout the cool temperate Northern Hemisphere in Asia, Europe, and in the southern Appalachian Mountains in the United States, but have been naturalized throughout the temperate climatic world.
The "Mayflower" Epigaea repens is a North American harbinger of May, and the floral emblem of both Nova Scotia and Massachusetts. Its native range extends from Newfoundland south to Florida, west to Kentucky in the southern range, and to Northwest Territories in the north.
April 29 to May 5 in Japan, which includes four different holidays, is called "Golden Week". Many workers have up to 10 days off. There is also 'May sickness', where new students or workers start to be tired of their new routine. (In Japan the school year and fiscal year start on April 1.)