Day

Day, Benjamin, 1838-1916, American printer; son of Benjamin Henry Day. While working in New York City, Day invented a process, utilizing celluloid sheets, for shading plates in the color printing of maps and illustrations. It is known as the Ben Day, or Benday, process. The term "Ben Day" is used as a noun, verb, and adjective.

Day, Benjamin Henry, 1810-89, American journalist. He learned the printer's trade in the office of the Springfield (Mass.) Republican and opened a printing office in New York City. Lack of work during a financial depression led him to begin publishing (1833) the New York Sun. The first edition consisted of four small pages; he wrote the paper and set the type without assistance. The price of the paper was 1¢; much less than other New York dailies at the time. The Sun was the first paper in the city to employ newsboys. By 1835, Day claimed a circulation of 19,360, the largest in the world, and in 1838 sold the Sun to his brother-in-law, Moses Yale Beach, for $40,000. In 1842, Day founded the monthly Brother Jonathan, which later became the first illustrated weekly in the United States.

Day, Clarence Shepard, 1874-1935, American essayist, b. New York City, grad. Yale, 1896. His biographical sketches of his parents, God and My Father (1932), Life with Father (1935), and Life with Mother (1937), won him popular recognition; incidents from these three books were used by Howard Lindsay and Russel Crouse for the play Life with Father (1939), which was one of the longest-running plays in Broadway history. Day's other works include essays, This Simian World (1920), and a collection of light verse and drawings, Scenes from the Mesozoic (1935).

Day, John, 1522-84, English printer. At his London shop Day designed and made type for himself, but not for sale. His types included musical notes and the first Anglo-Saxon type. He printed the first English book of church music (1560) and the first English edition of John Foxe's Book of Martyrs (1563), though not under that title (see Foxe, John). His edition of Euclid was the first English translation of that work. Day's printer's mark was a rising sun, a sleeper awakening, and the motto, "Arise, for it is Day."

Day, John, 1574?-1640?, English dramatist. Educated at Cambridge, he was one of Philip Henslowe's group of playwrights, collaborating with Thomas Dekker, Henry Chettle, and others. The allegorical masque The Parliament of Bees, which was written c.1607 (pub. 1641) is his only important work. His other plays include The Isle of Gulls (1606) and The Travels of Three English Brothers (1607).

Day, Stockwell, 1950-, Canadian political leader, b. Barrie, Ontario. He grew up in Montreal, attended (1970-71) the Univ. of Victoria, and held such jobs as auctioneer, deckhand, lumberjack, contractor, Christian educator, and evangelical lay pastor before entering politics. In 1986, Day was elected to the Alberta legislature, and subsequently served in several provincial offices, becoming Alberta's tax-cutting treasurer in 1997 and winning notice a proponent of a flat income tax, smaller government, and increased provincial sovereignty. In 2000 the youthful and vigorous Day defeated Preston Manning to become head of the Canadian Alliance and leader of the opposition; he was subsequently elected to the Canadian parliament. Day and the Alliance failed, however, to defeat the Liberals in elections called by Prime Minister Jean Chrétien for Nov., 2000. He resigned as party leader in Dec., 2001, and was replaced by Stephen Harper the following year. Day became minister for public safety in the Conservative government in 2006.

Day, Thomas, 1748-89, English social reformer and author. He supported the American Revolution and the abolition of slavery and was interested in improving the lot of the small farmer. His moralistic History of Sandford and Merton (3 vol., 1783-89) contrasts the "natural" education of the virtuous Sandford with the conventional one of the objectionable Merton. In Lichfield he was a member of the literary group centering about Anna Seward.

Day, William Rufus, 1849-1923, American statesman and Associate Justice of the U.S. Supreme Court (1903-22), b. Ravenna, Ohio. Admitted (1872) to the bar, Day practiced law in Ohio and served (1886-90) as judge of the court of common pleas. He became (1897) assistant to the Secretary of State and then (Apr., 1898) Secretary of State in the month when war was declared against Spain. He was successful in converting France and Germany from an attitude of seeming hostility to definite neutrality. Made chairman (Sept., 1898) of the U.S. commission to arrange peace after the Spanish-American War, he insisted upon purchase of the Philippines rather than claiming these islands by right of conquest. The treaty therefore provided for the payment of $20 million. Day became (1899) a judge of the U.S. Circuit Court of Appeals, and in 1903 President Theodore Roosevelt appointed him to the Supreme Court, where he generally voted for the dissolution of trusts and the preservation of states' rights.

day, period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun over a stationary observer's celestial meridian. The length of a solar day varies during the course of a year, so for purposes of time measurement an average, or mean, solar day is used (see solar time), equal to exactly 24 hr. The sidereal day, used by astronomers, is measured relative to the fixed stars rather than the sun (see sidereal time); it is about 4 min shorter than the mean solar day. The term day is also used to refer to that part of each 24-hr period during which the sun's direct rays are not blocked by the earth, this period of daylight hours extending from sunrise to sunset; the remaining portion of the 24 hr is called night. If the plane of the earth's orbit about the sun coincided with the plane of the equator, day and night would each be 12 hr long everywhere on the earth all year long. However, because of the tilt of the earth's axis of rotation, the times of sunrise and sunset vary from day to day, with the result that in the Northern Hemisphere there are long days and short nights in the summer and short days and long nights in the winter. See equinox; solstice.

or day lily

Any plant of the genus Hemerocallis, in the lily family, consisting of about 15 species of perennial herbaceous plants distributed from central Europe to eastern Asia. Members have long-stalked clusters of funnel- or bell-shaped flowers that range in colour from yellow to red and are each short-lived (hence “day” lily). Daylilies have fleshy roots and narrow, sword-shaped leaves that are grouped at the base of the plant. The fruit is a capsule. Some species are cultivated as ornamentals or for their edible flowers and buds.

Learn more about daylily with a free trial on Britannica.com.

Time required for a celestial body to turn once on its axis; especially, the period of the Earth's rotation. The sidereal day (see sidereal period) is the time required for the Earth to rotate once relative to the background of the stars (i.e., the time between two observed passages of a star over the same meridian of longitude). The apparent solar day is the time between two successive transits of the Sun over the same meridian. Because the orbital motion of the Earth makes the Sun seem to move slightly eastward each day relative to the stars, the solar day is about four minutes longer than the sidereal day. The mean solar day is the average value of the solar day, which changes slightly in length during the year as the Earth's speed in its orbit varies.

Learn more about day with a free trial on Britannica.com.

Lovers' holiday celebrated on February 14, the feast day of St. Valentine, one of two 3rd-century Roman martyrs of the same name. St. Valentine is considered the patron of lovers and especially of those unhappily in love. The feast day became a lovers' festival in the 14th century, probably as an extension of pagan love festivals and fertility rites celebrated in mid-February. Today it is marked by the exchange of romantic cards (valentines), flowers, and other gifts.

Learn more about Valentine's Day with a free trial on Britannica.com.

U.S. holiday. It originated in the autumn of 1621 when Plymouth governor William Bradford invited neighbouring Indians to join the Pilgrims for a three-day festival of recreation and feasting in gratitude for the bounty of the season, which had been partly enabled by the Indians' advice. Neither the standard Thanksgiving meal of turkey, cranberry sauce, and pumpkin pie nor the family orientation of the day reflects the Plymouth event, however. Proclaimed a national holiday in 1863, Thanksgiving is celebrated on the fourth Thursday in November (though it was moved back one week in 1939–41 to extend the Christmas shopping season). Canada adopted Thanksgiving as a national holiday in 1879; since 1957 it has been celebrated on the second Monday in October.

Learn more about Thanksgiving Day with a free trial on Britannica.com.

orig. Sandra Day

(born March 26, 1930, El Paso, Texas, U.S.) U.S. jurist. After graduating first in her law school class at Stanford University (1950), she entered private practice in Arizona. She served as an assistant state attorney general (1965–69) before being elected in 1969 to the state senate, where she became the first woman in the U.S. to hold the position of majority leader (1972–74). After serving on the superior court of Maricopa county and the state court of appeals, she was nominated in 1981 by Pres. Ronald Reagan to the Supreme Court of the United States, becoming the first female justice in the court's history. Known for her dispassionate and meticulously researched opinions, she proved to be a moderate and pragmatic conservative who sometimes sided with the court's liberal minority on social issues (e.g., abortion rights). O'Connor retired from the court in 2006.

Learn more about O'Connor, Sandra Day with a free trial on Britannica.com.

orig. Sandra Day

(born March 26, 1930, El Paso, Texas, U.S.) U.S. jurist. After graduating first in her law school class at Stanford University (1950), she entered private practice in Arizona. She served as an assistant state attorney general (1965–69) before being elected in 1969 to the state senate, where she became the first woman in the U.S. to hold the position of majority leader (1972–74). After serving on the superior court of Maricopa county and the state court of appeals, she was nominated in 1981 by Pres. Ronald Reagan to the Supreme Court of the United States, becoming the first female justice in the court's history. Known for her dispassionate and meticulously researched opinions, she proved to be a moderate and pragmatic conservative who sometimes sided with the court's liberal minority on social issues (e.g., abortion rights). O'Connor retired from the court in 2006.

Learn more about O'Connor, Sandra Day with a free trial on Britannica.com.

First day of the new year, celebrated with religious, cultural, and social observances around the world. It is usually marked by rites and ceremonies that symbolize casting off the old year and rejoicing in the new. Most of the world recognizes January 1 as the start of a new year because the Gregorian calendar, from its papal origin in 1582, has become the international reference for treaties, corporate contracts, and other legal documents. Nevertheless, numerous religious and national calendars have been retained. For example, in the Persian calendar (used in Iran and Afghanistan) New Year's Day falls on the spring equinox (March 20 or 21 in the Gregorian calendar). The more widely employed Islamic (Hijrī) calendar is based on 12 lunar months of 29 or 30 days; thus, the Islamic New Year's Day gradually regresses through the longer Gregorian calendar. The Hindu new year starts on the day following the first new moon on or after the spring equinox. The Chinese new year begins at sunset on the new moon in the sign of Aquarius (late January or early February). The Hebrew calendar is based on 12 lunar months (13 in certain years) of 29 or 30 days; the Jewish New Year's Day, or Rosh Hashanah, can fall anytime from September 6 to October 5 in the Gregorian calendar.

Learn more about New Year's Day with a free trial on Britannica.com.

or Decoration Day

U.S. holiday. Originally held (1868) in commemoration of soldiers killed in the American Civil War, its observance later extended to all U.S. war dead. Most states conform to the federal practice of observing it on the last Monday in May, but some retain the traditional day of celebration, May 30. National observance is marked by the placing of a wreath on the Tomb of the Unknowns in Arlington National Cemetery. Flags, insignia, and flowers are placed on the graves of veterans in local cemeteries.

Learn more about Memorial Day with a free trial on Britannica.com.

In Europe, the day (May 1) for traditional springtime celebrations. It probably originated in pre-Christian agricultural rituals. Celebrations included a May king and queen, a Maypole, and people carrying trees, green branches, or garlands. May Day was designated an international labour day by the International Socialist Congress of 1899, and it remains the standard Labour Day worldwide, with a few exceptions, including Canada and the U.S. A major holiday in the Soviet Union and other communist countries, it was the occasion for important political demonstrations.

Learn more about May Day with a free trial on Britannica.com.

Member of the Church of Jesus Christ of Latter-day Saints or of a sect closely related to it (e.g., the Community of Christ). The Mormon religion was founded by Joseph Smith, who claimed to have received an angelic vision telling him of the location of golden plates containing God's revelation; this he published in 1830 as the Book of Mormon. Smith and his followers accepted the Bible as well as the Mormon sacred scriptures but diverged significantly from orthodox Christianity, especially in their assertion that God exists in three distinct entities as Father, Son, and Holy Spirit. Mormons also believe that faithful members of the church will inherit eternal life as gods. Other unique doctrines include the belief in preexisting souls waiting to be born and in salvation of the dead through retroactive baptism. The church became notorious for its practice of polygamy, though it was officially sanctioned only between 1852 and 1890. Smith and his followers migrated from Palmyra, N.Y., to Ohio, Missouri, and finally Illinois, where Smith was killed by a mob in 1844. In 1846–47, under Brigham Young, the Mormons made a 1,100-mi (1,800-km) trek to Utah, where they founded Salt Lake City. In the early 21st century, the church had a worldwide membership of nearly 10 million, swelled yearly by the missionary work that church members, both men and women, are encouraged to perform.

Learn more about Mormon with a free trial on Britannica.com.

orig. Eleanora Fagan

(born April 7, 1915, Baltimore, Md., U.S.—died July 17, 1959, New York, N.Y.) U.S. jazz singer. She was “discovered” while she was singing in a Harlem nightclub in 1933. Recordings with Benny Goodman and Duke Ellington led to a series of outstanding small-group records (1935–42) featuring musicians such as Lester Young (who gave her the sobriquet Lady Day) and Teddy Wilson. Exposure with the big bands of Count Basie (1937) and Artie Shaw (1938) brought her greater public attention; for the rest of her life she would remain one of the best known of jazz singers. Among the songs identified with her were “Strange Fruit” and “God Bless the Child.” Personal crises and drug and alcohol addiction plagued her career, and she was incarcerated in 1947 on narcotics charges. Her voice could reveal a sweet, often sensual expressiveness or disturbing bitterness in the service of a lyric: her clear projection of emotion represents a landmark of personal expression.

Learn more about Holiday, Billie with a free trial on Britannica.com.

Annual holiday devoted to the recognition of working people's contribution to society. It is observed on the first Monday in September in the U.S. and Canada. It was first celebrated in New York City on Sept. 5, 1882, under the sponsorship of the Knights of Labor. Various U.S. states observed the holiday before 1894, when Congress passed a bill making Labor Day a national holiday. It is often celebrated with parades and speeches, as well as political rallies, and the day is sometimes the official kickoff date for national political campaigns in the U.S. In most other countries, workers are honoured on May Day.

Learn more about Labor Day with a free trial on Britannica.com.

or Fourth of July

Anniversary of the adoption of the U.S. Declaration of Independence by the Second Continental Congress (July 4, 1776). It is the greatest secular holiday in the country. Celebrating the day became common only after the War of 1812. Thereafter, civic-minded groups worked to link the ideals of democracy and citizenship to the patriotic spirit of the day.

Learn more about Independence Day with a free trial on Britannica.com.

formerly Dominion Day

Annual Canadian holiday. Observed on July 1, it commemorates the formation of the Dominion of Canada on July 1, 1867. With the 1982 passage of the Canada Act, its name was officially changed to Canada Day. It is celebrated with parades, fireworks, flag display, and the singing of the national anthem, “O Canada.”

Learn more about Canada Day with a free trial on Britannica.com.

(born April 27, 1904, Ballintubbert, County Leix, Ire.—died May 22, 1972, Hadley Wood, Hertfordshire, Eng.) Irish-born British poet. Son of a clergyman, Day-Lewis studied at the University of Oxford and in the 1930s became part of a circle of left-wing poets centred on W.H. Auden, though he later turned to an individual lyricism expressed in traditional forms. His works include translations of Virgil's Georgics (1940), Aeneid (1952), and Eclogues (1963) and the verse collections The Room (1965) and The Whispering Roots (1970). He also wrote the autobiography The Buried Day (1960) and several detective novels under the pseudonym Nicholas Blake. He became poet laureate of England in 1968. He was the father of actor Daniel Day-Lewis.

Learn more about Day-Lewis, C(ecil) with a free trial on Britannica.com.

English Day of Atonement

Jewish religious holiday, observed on the 10th day of the lunar month of Tishri (in late September or early October). It concludes the 10 days of repentance that begin with Rosh Hashanah. Its purpose is to purify the individual and community by forgiving the sins of others and by repenting one's own sins against God. Before the destruction of the Temple of Jerusalem, the high priest performed a sacrificial ceremony that concluded with the death of a scapegoat. Today it is marked by fasting and abstention from sex. Its eve, when the Kol Nidre is recited, and the entire day of Yom Kippur, are spent in prayer and meditation.

Learn more about Yom Kippur with a free trial on Britannica.com.

(born April 27, 1904, Ballintubbert, County Leix, Ire.—died May 22, 1972, Hadley Wood, Hertfordshire, Eng.) Irish-born British poet. Son of a clergyman, Day-Lewis studied at the University of Oxford and in the 1930s became part of a circle of left-wing poets centred on W.H. Auden, though he later turned to an individual lyricism expressed in traditional forms. His works include translations of Virgil's Georgics (1940), Aeneid (1952), and Eclogues (1963) and the verse collections The Room (1965) and The Whispering Roots (1970). He also wrote the autobiography The Buried Day (1960) and several detective novels under the pseudonym Nicholas Blake. He became poet laureate of England in 1968. He was the father of actor Daniel Day-Lewis.

Learn more about Day-Lewis, C(ecil) with a free trial on Britannica.com.

In the Roman Catholic church, a day commemorating all the Christians believed to be in purgatory. Celebrated on November 2, it was first established by Odilo (d. 1049), abbot of Cluny, in the 11th century, and it was widely celebrated by the 13th century. The date follows All Saints' Day, with the idea that remembering the saints in heaven should be followed by remembering the souls awaiting release from purgatory. Roman Catholic doctrine holds that the prayers of the faithful on earth will help cleanse these souls in order to prepare them for heaven.

Learn more about All Souls' Day with a free trial on Britannica.com.

In Christianity, a day commemorating all the saints of the church, known and unknown. It is celebrated on November 1 in the Western churches and on the first Sunday after Pentecost in the Eastern churches. The first general observance of All Saints' Day was ordered by Pope Gregory IV in 837. In medieval England the festival was called All Hallows, and its eve is still known as Halloween.

Learn more about All Saints' Day with a free trial on Britannica.com.

A day (symbol: d) is a unit of time equivalent to 24 hours and the duration of a single rotation of planet Earth with respect to the sun. It is not an SI unit but it is accepted for use with SI. It is the fundamental unit of time in the IAU system of units. The term comes from the Old English dæg. The word is also used to mean daytime, the period of daylight experienced once per day and alternating with night.

Definitions

The day has several definitions.

International System of Units (SI)

A day contains 86,400 SI seconds. Each second is currently defined as

… the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

Astronomy

A day of exactly 86,400 SI seconds is the fundamental unit of time in astronomy.

All planets have a rotation period relative to the fixed stars, commonly called their sidereal rotation periods.. For Earth this is 23hours and 56 minutes and 50 seconds. Earth also has a misnamed sidereal day, its rotation relative to its own precessing or moving mean vernal equinox, which is 8.4 ms smaller than its rotation period relative to the fixed stars. The rotation periods of the gas giants, which have no solid surface, are usually assumed to be the rotation of the magnetic fields residing in their deep interiors unless stated otherwise. Jupiter and Saturn also have specified equatorial and high latitude rotation periods for their cloud tops.

Colloquial

The word refers to various relatedly defined ideas, including the following:

• The period of light when the Sun is above the local horizon (i.e., the period from sunrise to sunset), opposed to night. See Daytime (astronomy).
• The full day covering a dark and a light period, beginning from the beginning of the dark period or from a point near the middle of the dark period.
• A full dark and light period, sometimes called a nychthemeron in English, from the Greek for night-day.
• The period from 06:00 to 18:00 or 21:00 or some other fixed clock period overlapping or set off from other periods such as "morning", "evening", or "night".
• The mostly regular interval of one awaking, usually in the morning (personal day).

Introduction

The word day is used for several different units of time based on the rotation of the Earth around its axis. The most important one follows the apparent motion of the Sun across the sky (solar day; see solar time). The reason for this apparent motion is the rotation of the Earth around its axis, as well as the revolution of the Earth in its orbit around the Sun.

A day, as opposed to night, is commonly defined as the period during which sunlight directly reaches the ground, assuming that there are no local obstacles. Two effects make days on average longer than nights. The Sun is not a point, but has an apparent size of about 32 minutes of arc. Additionally, the atmosphere refracts sunlight in such a way that some of it reaches the ground even when the Sun is below the horizon by about 34 minutes of arc. So the first light reaches the ground when the centre of the Sun is still below the horizon by about 50 minutes of arc. The difference in time depends on the angle at which the Sun rises and sets (itself a function of latitude), but amounts to almost seven minutes at least.

Ancient custom has a new day start at either the rising or setting of the Sun on the local horizon (Italian reckoning, for example) The exact moment of, and the interval between, two sunrises or two sunsets depends on the geographical position (longitude as well as latitude), and the time of year. This is the time as indicated by ancient hemispherical sundials.

A more constant day can be defined by the Sun passing through the local meridian, which happens at local noon (upper culmination) or midnight (lower culmination). The exact moment is dependent on the geographical longitude, and to a lesser extent on the time of the year. The length of such a day is nearly constant (24 hours ± 30 seconds). This is the time as indicated by modern sundials.

A further improvement defines a fictitious mean Sun that moves with constant speed along the celestial equator; the speed is the same as the average speed of the real Sun, but this removes the variation over a year as the Earth moves along its orbit around the Sun (due to both its velocity and its axial tilt).

The Earth's day has increased in length over time. The original length of one day, when the Earth was new about 4.5 billion years ago, was about six hours as determined by computer simulation. It was 21.9 hours 620 million years ago as recorded by rhythmites (alternating layers in sandstone). This phenomenon is due to tides raised by the Moon which slow Earth's rotation. Because of the way the second is defined, the mean length of a day is now about 86,400.002 seconds, and is increasing by about 1.7 milliseconds per century (an average over the last 2700 years). See tidal acceleration for details.

Leap seconds

The actual mean period of rotation of the earth with respect to the sun is slightly longer than the SI day of 86,400 seconds. It is more nearly 86,400.002 seconds. This additional time accumulates to about 0.7 s per year or about seven seconds every ten years, necessitating the addition of an extra second to the civil clock occasionally to retard it and keep it more closely synchronized to the apparent movement of the sun. By the middle of this century the amount of time to be added to the clock will increase to one second every year. This additional second is called a leap second. A civil clock day is typically 86,400 SI seconds long, but will be 86,401 s or 86,399 s long in the event of a leap second.

Leap seconds are announced in advance by the International Earth Rotation and Reference Systems Service which measures the Earth's rotation and determines whether a leap second is necessary. Leap seconds occur only at the end of a UTC month, and have only ever been inserted at the end of June 30 or December 31.

Astronomy

In astronomy, the sidereal day is also used; it is about 3 minutes 56 seconds shorter than the solar day, and close to the actual rotation period of the Earth, as opposed to the Sun's apparent motion. In fact, the Earth spins 366 times about its axis during a 365-day year, because the Earth's revolution about the Sun removes one apparent turn of the Sun about the Earth.

Boundaries of the day

For most diurnal animals, including Homo sapiens, the day naturally begins at dawn and ends at sunset. Humans, with their cultural norms and scientific knowledge, have supplanted Nature with several different conceptions of the day's boundaries. The Jewish day begins at either sunset or at nightfall (when three second-magnitude stars appear). Medieval Europe followed this tradition, known as Florentine reckoning: in this system, a reference like "two hours into the day" meant two hours after sunset and thus times during the evening need to be shifted back one calendar day in modern reckoning. Days such as Christmas Eve, Halloween, and the Eve of Saint Agnes are the remnants of the older pattern when holidays began the evening before. Present common convention is for the civil day to begin at midnight, that is 00:00 (inclusive), and last a full twenty-four hours until 24:00 (exclusive).

In ancient Egypt, the day was reckoned from sunrise to sunrise. Muslims fast from daybreak to sunset each day of the month of Ramadan. The "Damascus Document", copies of which were also found among the Dead Sea Scrolls, states regarding Sabbath observance that "No one is to do any work on Friday from the moment that the sun's disk stands distant from the horizon by the length of its own diameter," presumably indicating that the monastic community responsible for producing this work counted the day as ending shortly before the sun had begun to set. The Baha'i day begins and ends at sunset, for a calendar that has 19 days, in each of 19 months. The vernal equinox begins and ends the Baha'i year. Days in excess of 361 are called inter-calendar days.

In the United States, nights are named after the previous day, e.g. "Friday night" usually means the entire night between Friday and Saturday. This is the opposite of the Jewish pattern. Events starting at midnight are often announced as occurring the day before. TV-guides tend to list nightly programs at the previous day, although programming a VCR requires the strict logic of starting the new day at 00:00 (to further confuse the issue, VCRs set to the 12-hour clock notation will label this "12:00 AM"). Expressions like "today", "yesterday" and "tomorrow" become ambiguous during the night.

Validity of tickets, passes, etc., for a day or a number of days may end at midnight, or closing time, when that is earlier. However, if a service (e.g. public transport) operates from e.g. 6:00 to 1:00 the next day (which may be noted as 25:00), the last hour may well count as being part of the previous day (also for the arrangement of the timetable). For services depending on the day ("closed on Sundays", "does not run on Fridays", etc.) there is a risk of ambiguity. As an example, for the Dutch Railways, a day ticket is valid 28 hours, from 0:00 to 28:00 (i.e. 4:00 the next day). To give another example, the validity of a pass on London Regional Transport services is until the end of the "transport day" -- that is to say, until 4:30 am on the day after the "expiry" date stamped on the pass.

References

See also

• Day length
• Daylight
• Earth clock
• Season

External links

• Show where it is daytime at the moment
• Sunrise and sunset, all year long, anywhere
• Definitions of day, night, twilight (USA navy site)
• Formulas to calculate the length of day and night
• Dates by each calendar year