May is the fifth month of the year in the Julian and Gregorian calendars and the third of seven months to have 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. May (in Latin, Maius) was named for the Greek Goddess Maia, who was identified with the Roman era goddess of fertility, Bona Dea, whose festival was held in May. Conversely, the Roman poet Ovid provides a second etymology, in which he says that 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).
A month is a unit of time used with calendars, which is approximately as long as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of moon phases; such months (lunations) are synodic months and last approximately 29.53 days. Researchers have deduced that people counted days in relation to the Moon's phases from excavated tally sticks as early as the Paleolithic age.