Day in the context of "Nocturnality"

Time is the continuous progression of existence that occurs in an apparently irreversible succession from the past, through the present, and into the future. Time dictates all forms of action, age, and causality, being a component quantity of various measurements used to sequence events, to compare the duration of events (or the intervals between them), and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions.

Time is primarily measured in linear spans or periods, ordered from shortest to longest. Practical, human-scale measurements of time are performed using clocks and calendars, reflecting a 24-hour day collected into a 365-day year linked to the astronomical motion of the Earth. Scientific measurements of time instead vary from Planck time at the shortest to billions of years at the longest. Measurable time is believed to have effectively begun with the Big Bang 13.8 billion years ago, encompassed by the chronology of the universe. Modern physics understands time to be inextricable from space within the concept of spacetime described by general relativity. Time can therefore be dilated by velocity and matter to pass faster or slower for an external observer, though this is considered negligible outside of extreme conditions, namely relativistic speeds or the gravitational pulls of black holes.

A calendar is a system of organizing days. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single and specific day within such a system. A calendar is also a physical record (often paper) of such a system. A calendar can also mean a list of planned events, such as a court calendar, or a partly or fully chronological list of documents, such as a calendar of wills.

A holiday is a day or other period of time set aside for festivals or recreation. Public holidays are set by public authorities and vary by state or region. Religious holidays are set by religious organisations for their members and are often also observed as public holidays in religious majority countries. Some religious holidays, such as Christmas, have become secularised by part or all of those who observe them. In addition to secularisation, many holidays have become commercialised due to the growth of industry.

Holidays can be thematic, celebrating or commemorating particular groups, events, or ideas, or non-thematic, days of rest that do not have any particular meaning. In Commonwealth English, the term can refer to any period of rest from work, such as vacations or school holidays. In American English, "the holidays" typically refers to the period from Thanksgiving to New Year's (late November to January 1), which contains many important holidays in American culture.

Daytime or day as observed on Earth is the period of the day during which a given location experiences natural illumination from direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. In direct sunlight the movement of the sun can be recorded and observed using a sundial that casts a shadow that slowly moves during the day. Other planets and natural satellites that rotate relative to a luminous primary body, such as a local star, also experience daytime, but this article primarily discusses daytime on Earth.

A sundial is a horological device that tells the time of day (referred to as civil time in modern usage) when direct sunlight shines by the apparent position of the Sun in the sky. In the narrowest sense of the word, it consists of a flat plate (the dial) and a gnomon, which casts a shadow onto the dial. As the Sun appears to move through the sky, the shadow aligns with different hour-lines, which are marked on the dial to indicate the time of day. The style is the time-telling edge of the gnomon, though a single point or nodus may be used. The gnomon casts a broad shadow; the shadow of the style shows the time. The gnomon may be a rod, wire, or elaborately decorated metal casting. The style must be parallel to the axis of the Earth's rotation for the sundial to be accurate throughout the year. The style's angle from horizontal is equal to the sundial's geographical latitude.

The term sundial can refer to any device that uses the Sun's altitude or azimuth (or both) to show the time. Sundials are valued as decorative objects, metaphors, and objects of intrigue and mathematical study.

The contrast of white and black (light and darkness, day and night) has a long tradition of metaphorical usage, traceable to the Ancient Near East, and explicitly in the Pythagorean Table of Opposites.In Western culture as well as in Confucianism, the contrast symbolizes the moral dichotomy of good and evil.

A calendar date is a reference to a particular day, represented within a calendar system, enabling a specific day to be unambiguously identified. Simple math can be performed between dates; commonly, the number of days between two dates may be calculated, e.g., "25 December 2025" is ten days after "15 December 2025". The date of a particular event depends on the time zone used to record it. For example, the air attack on Pearl Harbor that began at 7:48 a.m. local Hawaiian time (HST) on 7 December 1941 is recorded equally as having happened on 8 December at 3:18 a.m. Japan Standard Time (JST).

A particular day may be assigned a different nominal date according to the calendar used. The de facto standard for recording dates worldwide is the Gregorian calendar, the world's most widely used civil calendar. Many cultures use religious calendars such as the Gregorian (Western Christendom, AD), the Julian calendar (Eastern Christendom, AD), Hebrew calendar (Judaism, AM), the Hijri calendars (Islam, AH), or any other of the many calendars used around the world. Regnal calendars (that record a date in terms of years since the beginning of the monarch's reign) are also used in some places, for particular purposes.

A clock or chronometer is a device that measures and displays time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month, and the year. Devices operating on several physical processes have been used over the millennia.

Some predecessors to the modern clock may be considered "clocks" that are based on movement in nature: A sundial shows the time by displaying the position of a shadow on a flat surface. There is a range of duration timers, a well-known example being the hourglass. Water clocks, along with sundials, are possibly the oldest time-measuring instruments. A major advance occurred with the invention of the verge escapement, which made possible the first mechanical clocks around 1300 in Europe, which kept time with oscillating timekeepers like balance wheels.

In ecology, the term productivity refers to the rate of generation of biomass in an ecosystem, usually expressed in units of mass per volume (unit surface) per unit of time, such as grams per square metre per day (g m d). The unit of mass can relate to dry matter or to the mass of generated carbon. The productivity of autotrophs, such as plants, is called primary productivity, while the productivity of heterotrophs, such as animals, is called secondary productivity.

The productivity of an ecosystem is influenced by a wide range of factors, including nutrient availability, temperature, and water availability. Understanding ecological productivity is vital because it provides insights into how ecosystems function and the extent to which they can support life.

In meteorology, diurnal temperature variation is the variation between a high air temperature and a low temperature that occurs during the same day.

A week is a unit of time equal to seven days. It is the standard time period used for short cycles of days in most parts of the world. The days are often used to indicate common work days and rest days, as well as days of worship. Weeks are often mapped against yearly calendars. There are just over 52 weeks in a year. The term "week" may also be used to refer to a sub-section of the week, such as the workweek and weekend.

Ancient cultures had different "week" lengths, including ten days in Egypt and an eight-day week for Etruscans. The Etruscan week was adopted by the ancient Romans, but they later moved to a seven-day week, which had spread across Western Asia and the Eastern Mediterranean due to the influence of the Christian seven-day week, which is rooted in the Jewish seven-day week. In AD 321, Emperor Constantine the Great officially decreed a seven-day week in the Roman Empire, including making Sunday a public holiday. This later spread across Europe, then the rest of the world.

A month is a unit of time, used with calendars, that is approximately as long as a natural phase cycle of the Moon; the words month and Moon are cognates. The traditional concept of months arose with the cycle of Moon phases; such lunar months ("lunations") are synodic months and last approximately 29.53 days, making for roughly 12.37 such months in one Earth year. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months, based on the Moon's orbital period with respect to the Earth–Sun line, are still the basis of many calendars today and are used to divide the year.

Calendars that developed from the Roman calendar system, such as the internationally used Gregorian calendar, divide the year into 12 months, each of which lasts between 28 and 31 days. The names of the months were Anglicized from various Latin names and events important to Rome, except for the months 9–12, which are named after the Latin numerals 7–10 (septem, octo, novem, and decem) because they were originally the seventh through tenth months in the Roman calendar. In the modern Gregorian calendar, the only month with a variable number of days is the second month, February, which has 29 days during a leap year and 28 days otherwise.

The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is often used inclusively of the Julian calendar established by Julius Caesar in 46 BC.

According to most Roman accounts, their original calendar was established by their legendary first king Romulus. It consisted of ten months, beginning in spring with March and leaving winter as an unassigned span of days before the next year. These months each had 30 or 31 days and ran for 38 nundinal cycles, each forming a kind of eight-day week—nine days counted inclusively in the Roman manner—and ending with religious rituals and a public market. This fixed calendar bore traces of its origin as an observational lunar one. In particular, the most important days of each month—its kalends, nones, and ides—seem to have derived from the new moon, the first-quarter moon, and the full moon respectively. To a late date, the College of Pontiffs formally proclaimed each of these days on the Capitoline Hill and Roman dating counted down inclusively towards the next such day in any month. (For example, the year-end festival of Terminalia on 23 February was called VII. Kal. Mart., the 6th day before the March kalends.)

In the deep ocean, marine snow (also known as "ocean dandruff") is a continuous shower of mostly organic detritus falling from the upper layers of the water column. It is a significant means of exporting energy from the light-rich photic zone to the aphotic zone below, which is referred to as the biological pump. Export production is the amount of organic matter produced in the ocean by primary production that is not recycled (remineralised) before it sinks into the aphotic zone. Because of the role of export production in the ocean's biological pump, it is typically measured in units of carbon (e.g. mg C m d). The term was coined by explorer William Beebe as observed from his bathysphere. As the origin of marine snow lies in activities within the productive photic zone, the prevalence of marine snow changes with seasonal fluctuations in photosynthetic activity and ocean currents. Marine snow can be an important food source for organisms living in the aphotic zone, particularly for organisms that live very deep in the water column.

Morning is either the period from sunrise to noon, or the period from midnight to noon. In the first definition it is preceded by the twilight period of dawn, and there are no exact times for when morning begins (also true of evening and night) because it can vary according to one's latitude, and the hours of daylight at each time of year. However, morning strictly ends at noon, when afternoon starts.

Morning precedes afternoon, evening, and night in the sequence of a day. Originally, the term referred to sunrise.

Evening is the period of a day that begins at the end of afternoon and overlaps with the beginning of night. It starts when the sun is close to the horizon and overlaps both twilight and night. The exact times when evening begins and ends are subjective and depend on location and time of year. In some cases, evening is considered to begin during daylight; before sunset.

The adoption of the Gregorian Calendar has taken place in the history of most cultures and societies around the world, marking a change from one of various traditional (or "old style") dating systems to the contemporary (or "new style") system – the Gregorian calendar – which is widely used around the world today. Some states adopted the new calendar in 1582, others not before the early twentieth century, and others at various dates between. A few have yet to do so, but except for these, the Gregorian calendar is now the world's universal civil calendar, old style calendars remaining in use in religious or traditional contexts. During – and for some time after – the transition between systems, it has been common to use the terms "Old Style" and "New Style" when giving dates, to indicate which calendar was used to reckon them.

The Gregorian calendar was decreed in 1582 by the papal bull Inter gravissimas by Pope Gregory XIII, to correct an error in the Julian calendar that was causing an erroneous calculation of the date of Easter. The Julian calendar had been based upon a year lasting 365.25 days, but this was slightly too long; in reality, it is about 365.2422 days, and so over the centuries, the calendar had drifted increasingly out of alignment with the Earth's orbit. According to Gregory's scientific advisers, the calendar had acquired ten excess leap days since the First Council of Nicaea (which established the rule for dating Easter in AD 325). Consequently, he ruled, the numbering of days must jump by ten, to restore the status quo ante; thus, for example, when the Catholic countries of Europe adopted the new calendar, the day after Thursday, 4 October 1582 was Friday, 15 October 1582. Countries which did not change until the 18th century had by then observed an additional leap year (1700), necessitating the removal of eleven days from the reckoning. Some countries did not change until the 19th or 20th century, necessitating the removal of one or two further days.