May is the fifth month of the year in the Gregorian calendar. It contains 31 days and is a spring month in the Northern Hemisphere and an autumn month in the Southern Hemisphere. It is named after the Greek goddess Maia, who is associated with growth and fertility. May starts after April and before June.

In summary:

• May begins on May 1 and ends on May 31.
• It has 31 days.
• It is the last month of spring in the Northern Hemisphere.
• It is the last month of autumn in the Southern Hemisphere.
• Important celebrations include May Day (May 1) and Labor Day (May 1 in many countries).
• May is associated with the goddess Maia and has historical festivals centered on fertility and growth.

This covers the timing and general meaning of May. If "when is may" was asked to know about May's placement in the calendar, it is from the 1st of May to the 31st of May annually.