Month

A month is a unit of calendar time, usually one of twelve divisions of a year. Its length varies by calendar, from 28 to 31 days in the Gregorian calendar.

Calendar: A system for organizing days into units such as weeks, months, and years. A month is one of the units used to organize time in a calendar.
January: The first month of the Gregorian calendar, with 31 days. It exemplifies a fixed-length month in the standard civil calendar.
Roman calendar: The evolving calendar system used in ancient Rome before and during the development of the Julian calendar. Its reforms shaped the month sequence inherited by modern Western calendars.
Lunar calendar: A calendar whose months follow the Moon's phases, usually alternating between 29 and 30 days. Its months track lunar cycles rather than fixed positions in a solar year.
Year: A time interval used to track Earth's seasonal cycle or its orbit around the Sun. Most familiar calendars divide a year into twelve months.
February: The second month of the Gregorian calendar, with 28 days in common years and 29 in leap years. Its variable length shows how leap days alter a month's duration.
Julius Caesar: Roman political and military leader who introduced the Julian calendar in 46 BCE. His reform standardized a solar year and established month lengths close to modern ones.
Lunisolar calendar: A calendar that follows lunar months while periodically adding a month to stay aligned with the solar year. It combines moon-based months with seasonal adjustment.
Day: A unit of time based on Earth's rotation or the interval from one midnight to the next. Calendar months consist of whole days.
Leap year: A calendar year containing an added day to keep the calendar aligned with the solar year. The Gregorian calendar adds its leap day to February.

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