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 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.
The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon. This means that the lunar hemisphere facing Earth—the near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month.
Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, cosmological, calendrical, and astrological beliefs and practices of prehistory: vestiges of these are still found in astrology, a discipline long interwoven with public and governmental astronomy. It was not completely separated in Europe during the Copernican Revolution starting in 1543. In some cultures, astronomical data was used for astrological prognostication.
A lunar calendar is a calendar based on the monthly cycles of the Moon's phases, in contrast to solar calendars, whose annual cycles are based only directly on the solar year. The most widely observed purely lunar calendar is the Islamic calendar. A purely lunar calendar is distinguished from a lunisolar calendar, whose lunar months are brought into alignment with the solar year through some process of intercalation – such as by insertion of a leap month. The details of when months begin vary from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations.
A lunisolar calendar is a calendar in many cultures, combining lunar calendars and solar calendars. The date of Lunisolar calendars therefore indicates both the Moon phase and the time of the solar year, that is the position of the Sun in the Earth's sky. If the sidereal year is used instead of the solar year, then the calendar will predict the constellation near which the full moon may occur. As with all calendars which divide the year into months there is an additional requirement that the year have a whole number of months. In some case ordinary years consist of twelve months but every second or third year is an embolismic year, which adds a thirteenth intercalary, embolismic, or leap month.
A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.
The Metonic cycle or enneadecaeteris is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise observation the Metonic cycle defined as 235 synodic months is just 2 hours, 4 minutes and 58 seconds longer than 19 tropical years. Meton of Athens, in the 5th century BC, judged the cycle to be a whole number of days, 6,940. Using these whole numbers facilitates the construction of a lunisolar calendar.
The Mesolithic or Middle Stone Age is the Old World archaeological period between the Upper Paleolithic and the Neolithic. The term Epipaleolithic is often used synonymously, especially for outside northern Europe, and for the corresponding period in the Levant and Caucasus. The Mesolithic has different time spans in different parts of Eurasia. It refers to the final period of hunter-gatherer cultures in Europe and Middle East, between the end of the Last Glacial Maximum and the Neolithic Revolution. In Europe it spans roughly 15,000 to 5,000 BP; in the Middle East roughly 20,000 to 10,000 BP. The term is less used of areas farther east, and not at all beyond Eurasia and North Africa.
In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse.
A solar calendar is a calendar whose dates indicate the season or almost equivalently the apparent position of the Sun relative to the stars. The Gregorian calendar, widely accepted as a standard in the world, is an example of a solar calendar. The main other types of calendar are lunar calendar and lunisolar calendar, whose months correspond to cycles of Moon phases. The months of the Gregorian calendar do not correspond to cycles of the Moon phase.
The Hindu calendar, also called Panchanga, is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes. They adopt a similar underlying concept for timekeeping based on sidereal year for solar cycle and adjustment of lunar cycles in every three years, but differ in their relative emphasis to moon cycle or the sun cycle and the names of months and when they consider the New Year to start. Of the various regional calendars, the most studied and known Hindu calendars are the Shalivahana Shaka found in the Deccan region of Southern India and the Vikram Samvat (Bikrami) found in Nepal and the North and Central regions of India – both of which emphasize the lunar cycle. Their new year starts in spring. In regions such as Tamil Nadu and Kerala, the solar cycle is emphasized and this is called the Tamil calendar and Malayalam calendar and these have origins in the second half of the 1st millennium CE. A Hindu calendar is sometimes referred to as Panchangam (पञ्चाङ्गम्), which is also known as Panjika in Eastern India.
The ancient Egyptian calendar – a civil calendar – was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of five epagomenal days treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work.
The history of calendars covers practices with ancient roots as people created and used various methods to keep track of days and larger divisions of time. Calendars commonly serve both cultural and practical purposes and are often connected to astronomy and agriculture.
There are three related types of Neolithic earthwork that are all sometimes loosely called henges. The essential characteristic of all three is that they feature a ring-shaped bank and ditch, with the ditch inside the bank. Because the internal ditches would have served defensive purposes poorly, henges are not considered to have been defensive constructions. The three henge types are as follows, with the figure in brackets being the approximate diameter of the central flat area:
- Henge. The word henge refers to a particular type of earthwork of the Neolithic period, typically consisting of a roughly circular or oval-shaped bank with an internal ditch surrounding a central flat area of more than 20 m (66 ft) in diameter. There is typically little if any evidence of occupation in a henge, although they may contain ritual structures such as stone circles, timber circles and coves. Henge monument is sometimes used as a synonym for henge. Henges sometimes, but by no means always, featured stone or timber circles, and circle henge is sometimes used to describe these structures. The three largest stone circles in Britain are each within a henge. Examples of henges without significant internal monuments are the three henges of Thornborough Henges. Although having given its name to the word henge, Stonehenge is atypical in that the ditch is outside the main earthwork bank.
- Hengiform monument. Like an ordinary henge, except the central flat area is between 5 and 20 m (16–66 ft) in diameter, they comprise a modest earthwork with a fairly wide outer bank. The terms Mini henge or Dorchester henge are sometimes used as synonyms for hengiform monument. An example is the Neolithic site at Wormy Hillock Henge.
- Henge enclosure. A Neolithic ring earthwork with the ditch inside the bank, with the central flat area having abundant evidence of occupation and usually being more than 300 m (980 ft) in diameter. Some true henges are as large as this, but lack evidence of domestic occupation. Super henge is sometimes used as a synonym for a henge enclosure. However, sometimes Super henge is used to indicate size alone rather than use, e.g. "Marden henge ... is the least understood of the four British 'superhenges' ".
The Nebra sky disc is a bronze disc of around 30 cm (12 in) diameter and a weight of 2.2 kg (4.9 lb), having a blue-green patina and inlaid with gold symbols. These symbols are interpreted generally as the Sun or full moon, a lunar crescent, and stars. Two golden arcs along the sides are thought to mark the angle between the solstices. Another arc at the bottom with internal parallel lines is usually interpreted as a solar boat with numerous oars, though some authors have also suggested that it may represent a rainbow, the Aurora Borealis, a comet, or a sickle.
Durrington Walls is the site of a large Neolithic settlement and later henge enclosure located in the Stonehenge World Heritage Site in England. It lies 2 miles (3.2 km) north-east of Stonehenge in the parish of Durrington, just north of Amesbury in Wiltshire. The henge is the second-largest Late Neolithic palisaded enclosure known in the United Kingdom, after Hindwell in Wales.
A recumbent stone circle is a type of stone circle that incorporates a large monolith, known as a recumbent, lying on its side. They are found in only two regions: in Aberdeenshire in the north-east of Scotland and in the far south-west of Ireland in the counties of Cork and Kerry. In Ireland, the circles are now more commonly called Cork–Kerry or axial stone circles. They are believed by some archaeologists such as Aubrey Burl to be associated with rituals in which moonlight played a central role, as they are aligned with the arc of the southern moon. Recent excavations at Tomnaverie stone circle have suggested that no alignment of the circle was intended.
Mesha Sankranti refers to the first day of the solar cycle year, that is the solar New Year in the Hindu luni-solar calendar. The Hindu calendar also has a lunar new year, which is religiously more significant. The solar cycle year is significant in Assamese, Odia, Punjabi, Malayalam, Tamil, and Bengali calendars.
Vincent Gaffney is a British archaeologist and the Anniversary Chair in Landscape Archaeology at the University of Bradford.
An axial stone circle is a megalithic ring of stones of a particular design found in County Cork and County Kerry in southwest Ireland. Archaeologists have found it convenient to consider the axial five-stone circle and axial multiple-stone circle separately. The circle has an approximate axis of symmetry aligned in a generally northeast–southwest direction. The stone at the southwest side of the circle, rather than being an upright orthostat like all the rest, is a slab lying horizontally with its long thin edge along the circumference of the ring. Because it marks the axis of the circle it is called the axial stone.
