September 21

Characteristics and calendar position

As a fixed calendar date, September 21 does not correspond to an astronomical event every year; the autumnal equinox usually occurs a day or two later in the Northern Hemisphere. In civil and religious calendars it functions as a day for both secular and sacred observances, and its weekday shifts from year to year according to the standard leap-year cycle.

Notable observances and holidays

Several international and national observances fall on September 21. These include:

• International Day of Peace, designated by the United Nations and observed as a day devoted to strengthening the ideals of peace, both within and among all nations and peoples.
• World Alzheimer's Day, observed by Alzheimer’s organizations to raise awareness about dementia and support for caregivers.
• Belize Independence Day, marking the nation’s independence from British colonial rule in 1981.
• The Christian feast of Saint Matthew the Apostle in many Western liturgical calendars.

Historical events and significance

Across history, September 21 has seen a range of political, cultural and scientific events. On different years it has been the date of declarations, openings of institutions, and cultural milestones. The day is often chosen for international campaigns and commemorations because its late-September timing suits global calendars and media cycles.

Notable births

Several well-known cultural figures were born on September 21. Representative examples include:

• Leonard Cohen (poet, novelist and songwriter), a prominent Canadian artist.
• Stephen King (novelist), an American author known for his contributions to horror and speculative fiction.
• Bill Murray (actor and comedian), an American performer noted for film and television roles.

Context and distinctions

September 21 is both a routine calendar date and, in some years, a focal point for coordinated global action because of scheduled observances. Its mix of secular national holidays, religious feasts and international awareness days makes it a date that is recognized by governments, religious institutions, charities and cultural organizations around the world.

For further information on the calendar system and leap-year rules, see references to the Gregorian calendar and to the treatment of leap years.