day
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day,
period of timetime,sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophical and scientific, and biological.
..... Click the link for more information. 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 meridiancelestial meridian,
vertical circle passing through the north celestial pole and an observer's zenith. It is an axis in the altazimuth coordinate system.
..... Click the link for more information. . 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 timesolar time,
time defined by the position of the sun. The solar day is the time it takes for the sun to return to the same meridian in the sky. Local solar time is measured by a sundial.
..... Click the link for more information. ), equal to exactly 24 hr. The sidereal day, used by astronomers, is measured relative to the fixed stars rather than the sun (see sidereal timesidereal time
(ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on the observer's celestial meridian.
..... Click the link for more information. ); 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 equinoxequinox
, either of two points on the celestial sphere where the ecliptic and the celestial equator intersect. The vernal equinox, also known as "the first point of Aries," is the point at which the sun appears to cross the celestial equator from south to north.
..... Click the link for more information. ; solsticesolstice
[Lat.,=sun stands still], in astronomy, either of the two points on the ecliptic that lie midway between the equinoxes (separated from them by an angular distance of 90°).
..... Click the link for more information. .
day
The period of the Earth's rotation on its axis, equal to 86 400 seconds (24 hours) unless otherwise specified.Day
(1) The same as sutki (24 hours).
(2) The light portion of the 24-hour period, between the rising and setting of the upper edge of the sun. Its length depends on geographical latitude and varies with the declination of the sun. At the equator the length of the day is roughly constant and is equal to approximately 12 hrs. At the poles the day lasts half a year. At latitudes from 0° to + 66°37’ the length of the day is at a maximum at the summer solstice (June 22) and at a minimum at the winter solstice (December 22). On the other hand, at latitudes from 0° to -66°37’ the day is shortest on June 22 and longest on December 22. Beyond the polar circles (latitude greater than +66°37’ or less than -66°37’), the day lasts more than 24 hours (polar day), depending on the time of year (in the summer at the north pole and in the winter at the south pole). The length T of a day may be calculated from the formula cos t = -[sin(R + ρ) - sin δsin φ ]/(cos δ cos φ) T = 2t, where δ is the sun’s declination, φ the geographical latitude, R the sun’s angular radius (16’), and ρ the refraction at the horizon (34’). The length of the day between latitudes +34° and +64° on the 1st, 11th and 21st of each month is given in Table 1. The values are accurate to 2-3 minutes over the next 50. years.
E. A. IUROV
Table 1. Length of day at various latitudes of the northern hemisphere | ||||||
---|---|---|---|---|---|---|
Local latitude (north) | ||||||
Date | 34° hr min | 40° hr min | 46° hr min | 52° hr min | 58° hr min | 64° hr min |
January | ||||||
1............... | 9 54 | 9 23 | 8 43 | 7 51 | 6 36 | 4 27 |
11............... | 10 04 | 9 34 | 8 56 | 8 08 | 6 58 | 5 05 |
21............... | 10 16 | 9 49 | 9 15 | 8 32 | 7 31 | 5 59 |
February | ||||||
1............... | 10 34 | 10 10 | 9 42 | 9 06 | 8 18 | 7 06 |
11............... | 10 51 | 10 33 | 10 10 | 9 42 | 9 04 | 8 10 |
21............... | 11 10 | 10 58 | 10 40 | 10 21 | 9 53 | 9 16 |
March | ||||||
1............... | 11 27 | 11 18 | 11 06 | 10 52 | 10 33 | 10 08 |
11............... | 11 48 | 11 44 | 11 39 | 11 32 | 11 24 | 11 12 |
21............... | 12 10 | 12 12 | 12 12 | 12 12 | 12 15 | 12 18 |
April | ||||||
1............... | 12 32 | 12 38 | 12 48 | 12 57 | 13 10 | 13 28 |
11............... | 12 53 | 13 05 | 13 19 | 13 38 | 14 02 | 14 34 |
21............... | 13 13 | 13 30 | 13 51 | 14 16 | 14 50 | 15 40 |
May | ||||||
1............... | 13 32 | 13 54 | 14 21 | 14 52 | 15 37 | 16 46 |
11............... | 13 50 | 14 15 | 14 47 | 15 28 | 16 23 | 17 52 |
21 | 14 04 | 14 34 | 15 10 | 15 58 | 17 04 | 18 56 |
June | ||||||
1............... | 14 16 | 14 48 | 15 30 | 16 24 | 17 42 | 20 00 |
11............... | 14 23 | 14 58 | 15 42 | 16 38 | 18 04 | 20 44 |
21 | 14 26 | 15 01 | 15 46 | 16 45 | 18 11 | 21 00 |
July | ||||||
1............... | 14 23 | 14 58 | 15 42 | 16 40 | 18 03 | 20 45 |
11............... | 14 16 | 14 49 | 15 30 | 16 24 | 17 42 | 20 04 |
21............... | 14 06 | 14 36 | 15 14 | 16 02 | 17 10 | 19 07 |
August | ||||||
1............... | 13 50 | 14 16 | 14 48 | 15 29 | 16 29 | 17 58 |
11............... | 13 32 | 13 56 | 14 20 | 14 56 | 15 43 | 16 53 |
21............... | 13 14 | 13 32 | 13 53 | 14 20 | 14 55 | 15 48 |
September | ||||||
1............... | 12 53 | 13 05 | 13 20 | 13 38 | 14 03 | 14 36 |
11............... | 12 32 | 12 40 | 12 48 | 13 00 | 13 13 | 13 32 |
21............... | 12 12 | 12 14 | 12 17 | 12 20 | 12 23 | 12 28 |
October | ||||||
1............... | 11 50 | 11 47 | 11 44 | 11 40 | 11 34 | 11 24 |
11............... | 11 29 | 11 20 | 11 11 | 11 00 | 10 43 | 10 20 |
21............... | 11 09 | 10 56 | 10 40 | 10 20 | 9 54 | 9 15 |
November | ||||||
1............... | 10 49 | 10 29 | 10 06 | 9 39 | 9 01 | 8 05 |
11............... | 10 31 | 10 07 | 9 40 | 9 02 | 8 14 | 7 02 |
21............... | 10 16 | 9 48 | 9 15 | 8 32 | 7 33 | 6 01 |
December | ||||||
1............... | 10 04 | 9 34 | 8 56 | 8 08 | 6 59 | 5 06 |
11............... | 9 56 | 9 23 | 8 43 | 7 51 | 6 36 | 4 28 |
21............... | 9 54 | 9 20 | 8 38 | 7 45 | 6 28 | 4 12 |
Day
(holiday), a calendar date devoted to a historical event, labor holiday, international solidarity, and so on. Special days that have been established in the USSR are shown in Table 1.
The dates of observance of certain special days are associated with historical events—for example, the date established for Radio Day is associated with the 50th anniversary of the invention of radio by A. S. Popov (May 7, 1895). Miners’
Table 1. Special days of the USSR | ||
---|---|---|
Date of establishment | Date of observance | |
All-Union Farm Workers’ Day............... | Aug. 26, 1966 | second Sunday in October |
All-Union Petroleum and Gas Workers’ Day0............... | Aug. 28, 1965 | first Sunday in September |
All-Union Physical Education Day............... | June 16, 1939 | second Saturday in August |
All-Union Railroad Workers’ Day............... | July 28, 1936 | first Sunday in August |
Builders’ Day............... | Sept. 6, 1955 | second Sunday in August |
Chemists’ Day............... | Dec. 10, 1965 | last Sunday in May |
Cosmonautics Day; World Aviation and Cosmonautics Day............... | Apr. 9, 1962 | April 12 |
Electric Power Workers’ Day............... | May 23, 1966 | December 22 |
Fishermen’s Day............... | May 3, 1965 | second Sunday in July |
Food Industry Workers’ Day............... | Aug. 30, 1966 | third Sunday in October |
Forestry Workers’ Day............... | Aug. 13, 1966 | third Sunday in September |
Frontier Corps Day............... | May 15, 1958 | May 28 |
Geologists’ Day............... | Mar. 31,1966 | first Sunday in April |
Komsomol Foundation Day............... | 1918 | October 29 |
Light Industry Workers’ Day............... | May 30, 1966 | second Sunday in June |
Machine Builders’ Day............... | Aug. 15, 1966 | last Sunday in September |
Medical Workers’ Day............... | Dec. 10, 1965 | third Sunday in June |
Metallurgists’ Day............... | Sept. 28, 1957 | third Sunday in July |
Miners’ Day............... | Sept. 10, 1947 | last Sunday in August |
Paris Commune Day............... | Feb. 20, 1872 | March 18 |
Press Day............... | — | May5 |
Radio Day............... | May 2, 1945 | May 7 |
Rocket and Artillery Forces’ Day (before 1964, Artillery Day; established Oct. 21, 1944)............... | Nov. 17, 1964 | November 19 |
Soviet Army and Navy Day............... | — | February 23 |
Soviet Militia Day............... | Sept. 26, 1962 | November 10 |
Soviet Youth Day............... | Feb. 7, 1958 | last Sunday in June |
Tank Forces’ Day............... | July 11, 1946 | second Sunday in September |
Teachers’ Day............... | Sept. 29, 1965 | first Sunday in October |
Trade Workers ’ Day............... | June 29, 1966 | fourth Sunday in July |
USSR Air Force Day (Aviation Day)............... | Apr. 28, 1933 | third Sunday in August |
USSR Constitution Day............... | Dec. 5, 1936 | December 5 |
USSR Navy Day............... | July 22, 1939 | first Sunday after July 22 |
Victory Holiday............... | May 8, 1945 | May 9 |
V. I. Lenin Memorial Day............... | — | April 22 (V. I. Lenin’s birthday) |
V. I. Lenin Pioneer Organization Founding Day............... | 1922 | May 19 |
Day was first observed in connection with the night of Aug. 30-31, 1935, when the miner A. G. Stakhanov set a record that served as the beginning of the Stakhanovite movement; Electric Power Workers’ Day was established in honor of the opening day in 1920 of the All-Russian Congress of Soviets, which adopted GOELRO (State Commission for the Electrification of Russia).
Since 1955 it has become a tradition to hold a Poetry Day: each year during the autumn in major cities there are meetings of poets, critics, translators, actors, and readers. A collection entitled Poetry Day is usually published in observance of this day. Since 1957 a Film Day has been observed in Moscow and many other cities. This day usually is timed to coincide with the anniversary of Lenin’s decree on the nationalization of the motion-picture industry (Aug. 27, 1919).
Table 2. International special days | ||
---|---|---|
Dafe of establishment | Date of observance | |
African Liberation Day............... | 1963 | May 25 |
International Chess Day............... | July 20, 1966 | July 20 |
International Children’s Protection Day............... | 1949 | June 1 |
International Cooperation Day............... | 1923 | first Saturday in July |
International Journalists’ Solidarity Day............... | 1958 | September 8 |
International Students’ Day............... | 1950 | November 17 |
International Theater Day............... | June 10, 1961 | March 27 |
International Workers’ Solidarity Day—May Day............... | — | May 1 and 2 |
International Youth Solidarity Day............... | 1957 | April 24 |
March 8 International Women’s Day............... | 1910 | March 8 |
United Nations Day............... | Oct. 31, 1947 | October 24 |
World Sister Cities Day............... | 1963 | last Sunday in April |
World Health Day............... | 1948 | April 7 |
World Youth Day............... | November 1945 | November 10 |
Birds’ Day, a spring holiday for schoolchildren, has been observed since 1926 (March 24 or on one of the first Sundays in April). Mass construction of wooden birdhouses is carried out in preparation for the arrival of the birds. Harvest Day is observed in many regions of the country.
The USSR and several foreign countries observe worldwide and international special days, which are given in Table 2.
Day
a unit of time equal to 24 hours. A distinction is made between the sidereal day and the solar day. The sidereal day is the period of rotation of the earth relative to the vernal equinox. The solar day is the period of rotation of the earth relative to the sun.
The sidereal day is equal to the interval of time between two successive upper (or lower) transits of the vernal equinox. The moment at which this transit occurs is regarded as the beginning of the sidereal day—that is, as zero hour (hr) of sidereal time. A distinction is made between the apparent, or true, sidereal day and the mean sidereal day, depending on whether the true or mean vernal equinox is used: the motion of the true equinox is affected by precession and nutation, and the motion of the mean equinox is affected only by precession. As a result of the preces-sional motion of the vernal equinox, the mean sidereal day is 0.0084 sec shorter than the actual period of the earth’s rotation. The duration of the apparent sidereal day is not constant and varies continuously owing to nutation.
It is inconvenient to use sidereal days for the measurement of time, since they do not coincide with the alternation of day and night. Consequently, solar days are generally employed. The solar day is equal to the time interval between two successive upper or lower transits of the sun—that is, between two successive noons or midnights. As a result of the ellipticity of the earth’s orbit and the obliquity of the ecliptic, the time between two successive transits of the apparent, or true, sun—that is, the duration of the apparent, or true, solar day—is not constant. During the course of a year, the length of the apparent solar day varies from 24 hr 3 min 36 sec of sidereal time, in mid-September, to 24 hr 4 min 27 sec of sidereal time, in late December. To eliminate this variation, the mean length of the solar day over a year is used. Such a day is called the mean solar day and is equal to 24 hr 3 min 56.55536 sec of sidereal time. In civil time, the beginning of the mean solar day is the mean midnight, that is, the moment of the lower transit of the fictitious point on the celestial sphere known as the mean sun.
Like the mean solar day, the sidereal day is divided into hours, minutes, and seconds. The relation between the sidereal and solar units is as follows: one day, minute, or second of sidereal time is equal to 0.9972696 of the corresponding unit of mean solar time. The circumstance that the year does not contain a whole number of mean solar days is the principal difficulty encountered in the construction of the calendar.
REFERENCE
Spravochnoe rukovodstvo po nebesnoi mekhanike i astrodinamike. Edited by G. N. Duboshin. Moscow, 1971.What does it mean when you dream about daylight?
Daytime as opposed to nighttime represents the conscious mind as opposed to the unconscious. Seeing what we are doing. Can refer to one’s mood: a sunny day is bright and cheerful whereas an overcast day is different. The word “day” plays a role in many idioms, from “bad hair day” to “make my day.”
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