Calendar: Difference between revisions
Jump to navigation
Jump to search
imported>Nil NZ m Reverted 2 edits by 2600:1004:B319:4895:14BA:55FF:FEA9:99F1 (talk) to last revision by Citation bot |
imported>AndreJustAndre No edit summary |
||
| Line 1: | Line 1: | ||
{{Short description|System for organizing | {{Short description|System for organizing days}} | ||
{{About|the dating system|the physical object|Calendar ( | {{About|the dating system|the physical object|Calendar (publication)|other uses|Calendar (disambiguation)}} | ||
{{Redirect|📅|the unofficial holiday commonly represented by this emoji|World Emoji Day}} | {{Redirect|📅|the unofficial holiday commonly represented by this emoji|World Emoji Day}} | ||
{{Distinguish|Calender}} | {{Distinguish|Calender}} | ||
{{Globalize|2=Eurasia|3=the Near East|date=September 2022|talk=Talk:Calendar#Systemic bias towards Eurasian calendars}} | {{Globalize|2=Eurasia|3=the Near East|date=September 2022|talk=Talk:Calendar#Systemic bias towards Eurasian calendars}} | ||
{{Use dmy dates|date= | {{Use dmy dates|date=October 2025 |cs1-dates=ll}} | ||
{{Use American English | date = | {{Use American English | date = October 2025}} | ||
{{ | {{infobox calendar date today|all=true}} | ||
[[File:Kalender Indonesia.jpg|thumb|Modern day [[Indonesia]]n [[Gregorian calendar]] for a [[Catholic Church|Catholic]] [[Church (building)|church]]]] | [[File:Kalender Indonesia.jpg|thumb|Modern day [[Indonesia]]n [[Gregorian calendar]] for a [[Catholic Church|Catholic]] [[Church (building)|church]]]] | ||
[[File:Calendar (part of a set) MET DP-13486-011.jpg|thumb | [[File:Calendar (part of a set) MET DP-13486-011.jpg|thumb|British calendar, 1851, gilt bronze and [[malachite]], height: 20.3 cm, [[Metropolitan Museum of Art]] (New York City)]] | ||
A '''calendar''' is a system of organizing [[day]]s | A '''calendar''' is a system of organizing [[day]]s.<ref name="NASA eclipses">{{Cite web |title=Calendars and their History |url=https://eclipse.gsfc.nasa.gov/SEhelp/calendars.html |access-date=2026-03-13 |website=eclipse.gsfc.nasa.gov}}</ref> This is done by giving names to periods of [[time]], typically days, [[weeks]], [[month]]s and [[years]].<ref name="NASA eclipses" /><ref>{{Cite book |last=Guo |first=Rongxing |url=https://books.google.com/books?id=8QNbDwAAQBAJ&dq=A+calendar+is+a+system+of+organizing+days.+This+is+done+by+giving+names+to+periods+of+time,+typically+days,+weeks,+months+and+years.&pg=PA159 |title=Human-Earth System Dynamics: Implications to Civilizations |date=16 May 2018 |publisher=Springer |isbn=978-981-13-0547-4 |pages=159 |language=en}}</ref><ref>{{Cite book |last1=Bond |first1=Thomas |url=https://books.google.com/books?id=ADJEAgAAQBAJ&dq=A+calendar+is+a+system+of+organizing+days.+This+is+done+by+giving+names+to+periods+of+time,+typically+days,+weeks,+months+and+years.&pg=RA1-PA9 |title=Singapore PSLE Mathematics Challenging Practice Solutions (Yellowreef) |last2=Hughes |first2=Chris |date=3 December 2013 |publisher=Yellowreef Limited |isbn=978-0-7978-0222-3 |language=en}}</ref> A [[calendar date|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.<ref>{{Cite web |date=2026-03-03 |title=CALENDAR definition and meaning {{!}} Collins English Dictionary |url=https://www.collinsdictionary.com/dictionary/english/calendar |access-date=2026-03-13 |website=www.collinsdictionary.com |language=en}}</ref> 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. | ||
Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the [[solar calendar|sun]] or the [[lunar calendar|moon]].<ref>{{Cite web |date=2021 | Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the [[solar calendar|sun]] or the [[lunar calendar|moon]].<ref>{{Cite web |date=12 February 2021 |title=Do menstrual and lunar cycles synchronize? What scientists say |url=https://www.medicalnewstoday.com/articles/menstrual-cycles-and-lunar-cycles-is-there-a-link |access-date=12 March 2024 |website=www.medicalnewstoday.com |language=en}}</ref><ref name="Introduction to Calendars">{{Cite web |title=Introduction to Calendars |url=https://aa.usno.navy.mil/faq/calendars |access-date=12 March 2024 |website=aa.usno.navy.mil}}</ref><ref>{{Cite web |title=History – Ancient Egyptian Calendar |url=https://mabscross.co.uk/wp-content/uploads/2020/06/3.-History-Calendar.pdf |access-date=12 March 2024 |archive-date=12 March 2024 |archive-url=https://web.archive.org/web/20240312074831/https://mabscross.co.uk/wp-content/uploads/2020/06/3.-History-Calendar.pdf |url-status=dead }}</ref> The most common type of pre-modern calendar was the [[lunisolar calendar]], a lunar calendar that occasionally adds one [[intercalary month]] to remain synchronized with the [[solar year]] over the long term. | ||
==Etymology== | ==Etymology== | ||
The term ''calendar'' is taken from {{lang|la|[[calends|kalendae]]}},<ref>{{Cite book |last=Ma'Atnefert |first=Mwt Seshatms Nkatraet |url=https://books.google.com/books?id=C7KnAgAAQBAJ&dq=The+term+calendar+is+taken+from+kalendae,&pg=PA9 |title=You are Harmony ... Take Time to Harmonize ... Calendars and Time Connecting |date=2011 |publisher=Lulu.com |isbn=978-1-257-10758-2 |pages=9 |language=en}}</ref><ref>{{Cite book |last=Lewis |first=James R. |url=https://books.google.com/books?id=qQFlCwAAQBAJ&dq=The+term+calendar+is+taken+from+kalendae,&pg=PA459 |title=The Astrology Book: The Encyclopedia of Heavenly Influences |date=2003 | The term ''calendar'' is taken from {{lang|la|[[calends|kalendae]]}},<ref>{{Cite book |last=Ma'Atnefert |first=Mwt Seshatms Nkatraet |url=https://books.google.com/books?id=C7KnAgAAQBAJ&dq=The+term+calendar+is+taken+from+kalendae,&pg=PA9 |title=You are Harmony ... Take Time to Harmonize ... Calendars and Time Connecting |date=2011 |publisher=Lulu.com |isbn=978-1-257-10758-2 |pages=9 |language=en}}</ref><ref>{{Cite book |last=Lewis |first=James R. |url=https://books.google.com/books?id=qQFlCwAAQBAJ&dq=The+term+calendar+is+taken+from+kalendae,&pg=PA459 |title=The Astrology Book: The Encyclopedia of Heavenly Influences |date=1 March 2003 |publisher=Visible Ink Press |isbn=978-1-57859-246-3 |pages=459 |language=en}}</ref> the term for the first day of the month in the Roman calendar, related to the verb {{lang|la|calare}} 'to call out', referring to the "calling" of the new moon when it was first seen.<ref>'' New Shorter Oxford English Dictionary''</ref> Latin {{lang|la|calendarium}} meant 'account book, register' (as accounts were settled and debts were collected on the calends of each month).<ref name="Sayeed-2019">{{Cite book |last=Sayeed |first=Ahmed |url=https://books.google.com/books?id=GVeoDwAAQBAJ&dq=Latin+calendarium+meant+'account+book,+register'&pg=PT408 |title=You Must Win: The winner can create History |date=10 August 2019 |publisher=Prowess Publishing |isbn=978-1-5457-4730-8 |language=en}}</ref> The Latin term was adopted in [[Old French]] as {{lang|fro|calendrier}} and from there in [[Middle English]] as {{lang|enm|calender}} by the 13th century (the spelling ''calendar'' is early modern).<ref name="Sayeed-2019" /> | ||
== History == | == History == | ||
| Line 26: | Line 26: | ||
The first recorded physical calendars, dependent on the development of [[Bronze Age writing|writing]] in the [[Ancient Near East]], are the [[Bronze Age]] [[Egyptian calendar|Egyptian]] and [[Sumerian calendar|Sumerian]] calendars.<ref>{{Cite journal|last=Shirley|first=Lawrence|date=11 February 2009|title=The Mayan and Other Ancient Calendars|url=http://dx.doi.org/10.4169/loci003264|location=Washington, DC|doi=10.4169/loci003264|journal=Convergence|doi-broken-date=1 July 2025 |access-date=16 March 2021|archive-date=9 April 2023|archive-url=https://web.archive.org/web/20230409163211/https://www.maa.org/press/periodicals/convergence/the-mayan-and-other-ancient-calendars|url-status=live|url-access=subscription}}</ref> | The first recorded physical calendars, dependent on the development of [[Bronze Age writing|writing]] in the [[Ancient Near East]], are the [[Bronze Age]] [[Egyptian calendar|Egyptian]] and [[Sumerian calendar|Sumerian]] calendars.<ref>{{Cite journal|last=Shirley|first=Lawrence|date=11 February 2009|title=The Mayan and Other Ancient Calendars|url=http://dx.doi.org/10.4169/loci003264|location=Washington, DC|doi=10.4169/loci003264|journal=Convergence|doi-broken-date=1 July 2025 |access-date=16 March 2021|archive-date=9 April 2023|archive-url=https://web.archive.org/web/20230409163211/https://www.maa.org/press/periodicals/convergence/the-mayan-and-other-ancient-calendars|url-status=live|url-access=subscription}}</ref> | ||
During the [[Vedic period]] India developed a sophisticated timekeeping methodology and calendars for [[Vedas|Vedic]] rituals.<ref>{{Cite book|last=Plofker|first=Kim|title=Mathematics in India|publisher=Princeton University Press|year=2009|isbn=978-0-691-12067-6|pages=10, 35–36, 67}}</ref> According to Yukio Ohashi, the Vedanga calendar in ancient India was based on astronomical studies during the Vedic Period and was not derived from other cultures.<ref>{{Cite book|last=Andersen|first=Johannes|url=https://books.google.com/books?id=gQYscrT0fgQC|title=Highlights of Astronomy, Volume 11B: As Presented at the XXIIIrd General Assembly of the IAU, 1997|date=31 January 1999|publisher=Springer Science & Business Media|isbn=978-0-7923-5556-4|pages=719|language=en|access-date=12 March 2021|archive-date=11 January 2023|archive-url=https://web.archive.org/web/20230111163620/https://books.google.com/books?id=gQYscrT0fgQC|url-status=live}}</ref> | During the [[Vedic period]] India developed a sophisticated timekeeping methodology and calendars for [[Vedas|Vedic]] rituals.<ref>{{Cite book|last=Plofker|first=Kim|author-link=Kim Plofker|title=Mathematics in India|title-link=Mathematics in India (book)|publisher=Princeton University Press|year=2009|isbn=978-0-691-12067-6|pages=10, 35–36, 67}}</ref> According to Yukio Ohashi, the Vedanga calendar in ancient India was based on astronomical studies during the Vedic Period and was not derived from other cultures.<ref>{{Cite book|last=Andersen|first=Johannes|url=https://books.google.com/books?id=gQYscrT0fgQC|title=Highlights of Astronomy, Volume 11B: As Presented at the XXIIIrd General Assembly of the IAU, 1997|date=31 January 1999|publisher=Springer Science & Business Media|isbn=978-0-7923-5556-4|pages=719|language=en|access-date=12 March 2021|archive-date=11 January 2023|archive-url=https://web.archive.org/web/20230111163620/https://books.google.com/books?id=gQYscrT0fgQC|url-status=live}}</ref> | ||
A large number of calendar systems in the Ancient Near East were based on the [[Babylonian calendar]] dating from the [[Iron Age]],<ref>{{Cite book |url=https://books.google.com/books?id=cg0OAQAAMAAJ&q=A+large+number+of+calendar+systems+in+the+Ancient+Near+East+were+based+on+the+Babylonian+calendar+dating+from+the+Iron+Age |title=Civilizations of the Ancient Near East |date=1995 |publisher=Scribner |isbn=978-0-684-19279-6 |language=en}}</ref> among them the calendar system of the Persian Empire, which in turn gave rise to the [[Zoroastrian calendar]] and the [[Hebrew calendar]].<ref>{{Cite web |date=2021 | A large number of calendar systems in the Ancient Near East were based on the [[Babylonian calendar]] dating from the [[Iron Age]],<ref>{{Cite book |url=https://books.google.com/books?id=cg0OAQAAMAAJ&q=A+large+number+of+calendar+systems+in+the+Ancient+Near+East+were+based+on+the+Babylonian+calendar+dating+from+the+Iron+Age |title=Civilizations of the Ancient Near East |date=1995 |publisher=Scribner |isbn=978-0-684-19279-6 |language=en}}</ref> among them the calendar system of the Persian Empire, which in turn gave rise to the [[Zoroastrian calendar]] and the [[Hebrew calendar]].<ref>{{Cite web |date=12 September 2021 |title=Egyptians celebrate new Egyptian year on September 11 |url=https://www.egypttoday.com/Article/4/107766/Egyptians-celebrate-new-Egyptian-year-on-September-11 |access-date=12 March 2024 |website=EgyptToday}}</ref><ref>{{Cite book |last=Sayeed |first=Ahmed |url=https://books.google.com/books?id=GVeoDwAAQBAJ&dq=calendar+system+of+the+Persian+Empire,+which+in+turn+gave+rise+to+the+Zoroastrian+calendar+and+the+Hebrew+calendar.&pg=PT407 |title=You Must Win: The winner can create History |date=10 August 2019 |publisher=Prowess Publishing |isbn=978-1-5457-4730-8 |language=en}}</ref> | ||
A great number of [[Hellenic calendars]] were developed in [[Classical Greece]], and during the [[Hellenistic period]] they gave rise to the ancient [[Roman calendar]] and to various [[Hindu calendars]].<ref>{{Cite web|title=Calendar - The Early Roman Calendar|url=https://www.britannica.com/science/calendar|access-date=19 January 2021|date=24 December 2020|website=Encyclopedia Britannica|language=en|archive-date=4 January 2021|archive-url=https://web.archive.org/web/20210104181246/https://www.britannica.com/science/calendar|url-status=live}}</ref> | A great number of [[Hellenic calendars]] were developed in [[Classical Greece]], and during the [[Hellenistic period]] they gave rise to the ancient [[Roman calendar]] and to various [[Hindu calendars]].<ref>{{Cite web|title=Calendar - The Early Roman Calendar|url=https://www.britannica.com/science/calendar|access-date=19 January 2021|date=24 December 2020|website=Encyclopedia Britannica|language=en|archive-date=4 January 2021|archive-url=https://web.archive.org/web/20210104181246/https://www.britannica.com/science/calendar|url-status=live}}</ref> | ||
| Line 34: | Line 34: | ||
Calendars in antiquity were [[lunisolar]], depending on the introduction of [[intercalary month]]s to align the solar and the lunar years. This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century [[Coligny calendar]]. | Calendars in antiquity were [[lunisolar]], depending on the introduction of [[intercalary month]]s to align the solar and the lunar years. This was mostly based on observation, but there may have been early attempts to model the pattern of intercalation algorithmically, as evidenced in the fragmentary 2nd-century [[Coligny calendar]]. | ||
The [[Roman calendar]] was reformed by [[Julius Caesar]] in 46 BC.<ref>{{cite web|title=The History of the Calendar|url=https://www.calendar.com/history-of-the-calendar/ |archive-url=https://web.archive.org/web/20201202131025/https://www.calendar.com/history-of-the-calendar/ |archive-date=2020 | The [[Roman calendar]] was reformed by [[Julius Caesar]] in 46 BC.<ref>{{cite web|title=The History of the Calendar|url=https://www.calendar.com/history-of-the-calendar/ |archive-url=https://web.archive.org/web/20201202131025/https://www.calendar.com/history-of-the-calendar/ |archive-date=2 December 2020 |url-status=dead}}</ref> His "Julian" calendar was no longer dependent on the observation of the new moon, but followed an algorithm of introducing a leap day every four years. This created a dissociation of the calendar [[month]] from [[lunation]]. The [[Gregorian calendar]], introduced in 1582, corrected most of the remaining difference between the Julian calendar and the solar year. | ||
The [[Islamic calendar]] is based on the prohibition of intercalation (''[[nasi']]'') by [[Muhammad]], in Islamic tradition dated to a sermon given on 9 [[Dhu al-Hijjah]] AH 10 (Julian date: 6 March 632). This resulted in an observation-based lunar calendar that shifts relative to the seasons of the solar year. | The [[Islamic calendar]] is based on the prohibition of intercalation (''[[nasi']]'') by [[Muhammad]], in Islamic tradition dated to a sermon given on 9 [[Dhu al-Hijjah]] AH 10 (Julian date: 6 March 632). This resulted in an observation-based lunar calendar that shifts relative to the seasons of the solar year. | ||
| Line 41: | Line 41: | ||
== Systems == | == Systems == | ||
[[Image:Universal Calendar including a meton cycle.svg | [[Image:Universal Calendar including a meton cycle.svg|thumb|A universal calendar, combining different calendars]] | ||
A full calendar system has a different calendar date for every day.<ref>{{Cite book |last=Onlineverdan |url=https://books.google.com/books?id=f3uMDwAAQBAJ&dq=A+full+calendar+system+has+a+different+calendar+date+for+every+day&pg=SA10-PA6 |title=APTITUDE & REASONING for GATE & ESE 2020 |publisher=Infinity Educations |isbn=978-81-940294-3-4 |pages=10–6 |language=en}}</ref><ref>{{Cite book |last=Jain |first=Hemant |url=https://books.google.com/books?id=G4yEDwAAQBAJ&dq=A+full+calendar+system+has+a+different+calendar+date+for+every+day&pg=SA8-PA5 |title=RRB Junior Engineer (2019) - MATHEMATICS for 1st STAGE CBT |date=2019 | A full calendar system has a different calendar date for every day.<ref>{{Cite book |last=Onlineverdan |url=https://books.google.com/books?id=f3uMDwAAQBAJ&dq=A+full+calendar+system+has+a+different+calendar+date+for+every+day&pg=SA10-PA6 |title=APTITUDE & REASONING for GATE & ESE 2020 |publisher=Infinity Educations |isbn=978-81-940294-3-4 |pages=10–6 |language=en}}</ref><ref>{{Cite book |last=Jain |first=Hemant |url=https://books.google.com/books?id=G4yEDwAAQBAJ&dq=A+full+calendar+system+has+a+different+calendar+date+for+every+day&pg=SA8-PA5 |title=RRB Junior Engineer (2019) - MATHEMATICS for 1st STAGE CBT |date=21 January 2019 |publisher=Infinity Educations |isbn=978-81-939356-9-9 |pages=8–5 |language=en}}</ref> Thus the week cycle is by itself not a full calendar system;<ref>{{Cite book |last=Jain |first=Hemant |url=https://books.google.com/books?id=G4yEDwAAQBAJ&dq=Thus+the+week+cycle+is+by+itself+not+a+full+calendar+system&pg=SA8-PA5 |title=RRB Junior Engineer (2019) - MATHEMATICS for 1st STAGE CBT |date=21 January 2019 |publisher=Infinity Educations |isbn=978-81-939356-9-9 |pages=8–5 |language=en}}</ref> neither is a system to name the days within a year without a system for identifying the years. | ||
The simplest calendar system just counts time periods from a reference date, or '''[[epoch]]'''.<ref>{{Cite book |last=Jain |first=Hemant |url=https://books.google.com/books?id=G4yEDwAAQBAJ&dq=The+simplest+calendar+system+just+counts+time+periods+from+a+reference+date.&pg=SA8-PA6 |title=RRB Junior Engineer (2019) - MATHEMATICS for 1st STAGE CBT |date=2019 | The simplest calendar system just counts time periods from a reference date, or '''[[epoch]]'''.<ref>{{Cite book |last=Jain |first=Hemant |url=https://books.google.com/books?id=G4yEDwAAQBAJ&dq=The+simplest+calendar+system+just+counts+time+periods+from+a+reference+date.&pg=SA8-PA6 |title=RRB Junior Engineer (2019) - MATHEMATICS for 1st STAGE CBT |date=21 January 2019 |publisher=Infinity Educations |isbn=978-81-939356-9-9 |pages=8–6 |language=en}}</ref> This applies for the [[Julian day]] or [[Unix Time]]. Virtually the only possible variation is using a different reference date, in particular, one less distant in the past to make the numbers smaller. Computations in these systems are just a matter of addition and subtraction. | ||
Other calendars have one (or multiple) larger units of time. | Other calendars have one (or multiple) larger units of time. | ||
| Line 58: | Line 58: | ||
Cycles can be synchronized with periodic phenomena: | Cycles can be synchronized with periodic phenomena: | ||
[[File:Sun and Moon Nuremberg chronicle.jpg | [[File:Sun and Moon Nuremberg chronicle.jpg|thumbnail|[[Sun]] and [[Moon]], Schedel's Nuremberg Chronicle, 1493]] | ||
* [[Lunar calendar]]s are synchronized to the motion of the Moon ([[lunar phase]]s); an example is the Islamic calendar. | * [[Lunar calendar]]s are synchronized to the motion of the Moon ([[lunar phase]]s); an example is the Islamic calendar. | ||
* [[Solar calendar]]s are based on perceived [[seasonal year|seasonal]] changes synchronized to the apparent motion of the Sun; an example is the [[Persian calendar]]. | * [[Solar calendar]]s are based on perceived [[seasonal year|seasonal]] changes synchronized to the apparent motion of the Sun; an example is the [[Persian calendar]]. | ||
| Line 71: | Line 71: | ||
{{main|Solar calendar}} | {{main|Solar calendar}} | ||
Solar calendars assign a ''date'' to each [[solar time|solar day]] | Solar calendars assign a ''date'' to each [[solar time|solar day]],<ref name="Introduction to Calendars"/> which is based on the apparent motion of the Sun. A day may consist of the period between [[sunrise]] and [[sunset]], with a following period of [[night]], or it may be a period between successive events such as two sunsets.<ref>{{Cite book |url=https://books.google.com/books?id=drMzAQAAMAAJ&dq=A+day+may+consist+of+the+period+between+sunrise+and+sunset,+with+a+following+period+of+night&pg=PA983 |title=The Jurist |date=1861 |publisher=S. Sweet |pages=983 |language=en}}</ref><ref>{{Cite book |last=Oxossi |first=Diego de |url=https://books.google.com/books?id=FN11EAAAQBAJ&dq=A+day+may+consist+of+the+period+between+sunrise+and+sunset,+with+a+following+period+of+night&pg=PT37 |title=Sacred Leaves: A Magical Guide to Orisha Herbal Witchcraft |date=8 July 2022 |publisher=Llewellyn Worldwide |isbn=978-0-7387-6721-5 |language=en}}</ref> The length of the interval between two such successive events may vary slightly during the year, or it may be averaged into a [[solar time|mean solar day]]. Other types of calendar may also use a solar day. | ||
The Egyptians appear to have been the first to develop a solar calendar,<ref>{{Cite web |title=Solar calendar {{!}} Ancient Egypt, Mayan, Aztec {{!}} Britannica |url=https://www.britannica.com/science/solar-calendar |access-date=2024 | The Egyptians appear to have been the first to develop a solar calendar,<ref>{{Cite web |title=Solar calendar {{!}} Ancient Egypt, Mayan, Aztec {{!}} Britannica |url=https://www.britannica.com/science/solar-calendar |access-date=12 March 2024 |website=www.britannica.com |language=en}}</ref> using as a fixed point the annual sunrise reappearance of the Dog Star—[[Sirius]], or Sothis—in the eastern sky, which coincided with the annual flooding of the Nile River.<ref>{{Cite book |url=https://books.google.com/books?id=mXsoAQAAIAAJ&q=The+Egyptians+appear+to+have+been+the+first+to+develop+a+solar+calendar, |title=The New Encyclopædia Britannica: Micropædia |date=1991 |publisher=Encyclopædia Britannica |isbn=978-0-85229-529-8 |pages=941 |language=en}}</ref><ref>{{Cite book |last=Lawson |first=Russell M. |url=https://books.google.com/books?id=kwTHEAAAQBAJ&dq=The+Egyptians+appear+to+have+been+the+first+to+develop+a+solar+calendar,&pg=PT179 |title=Science in the Ancient World: From Antiquity through the Middle Ages |date=23 September 2021 |publisher=Bloomsbury Publishing USA |isbn=979-8-216-14241-6 |language=en}}</ref><ref>{{Cite book |last=Muntz |first=Charles |url=https://books.google.com/books?id=VGHODQAAQBAJ&dq=The+Egyptians+appear+to+have+been+the+first+to+develop+a+solar+calendar,&pg=PT16 |title=Diodorus Siculus and the World of the Late Roman Republic |date=2 January 2017 |publisher=Oxford University Press |isbn=978-0-19-064901-2 |language=en}}</ref> They built a calendar with 365 days, divided into 12 months of 30 days each, with 5 extra days at the end of the year. However, they did not include the extra bit of time in each year, and this caused their calendar to slowly become inaccurate.<ref>{{Cite web |title=Solar calendar | chronology | Britannica |url=https://www.britannica.com/science/solar-calendar}}</ref> | ||
===Lunar=== | ===Lunar=== | ||
{{Main|Lunar calendar}} | {{Main|Lunar calendar}} | ||
Not all calendars use the solar year as a unit. A lunar calendar is one in which days are numbered within each [[lunar phase]] cycle. Because the length of the [[lunar month]] is not an even fraction of the length of the [[tropical year]], a purely lunar calendar quickly drifts against the seasons, which do not vary much near the equator. It does, however, stay constant with respect to other phenomena, notably [[tide]]s. An example is the [[Islamic calendar]]. | Not all calendars use the solar year as a unit. A lunar calendar is one in which days are numbered within each [[lunar phase]] cycle. Because the length of the [[lunar month]] is not an even fraction of the length of the [[tropical year]], a purely lunar calendar quickly drifts against the seasons, which do not vary much near the equator. It does, however, stay constant with respect to other phenomena, notably [[tide]]s. An example is the [[Islamic calendar]]. | ||
Alexander Marshack, in a controversial reading,<ref>James Elkins, ''[https://books.google.com/books?id=5Ku6YdWurMgC&pg=PA63&lpg=PA63 Our beautiful, dry, and distant texts]'' (1998) 63ff.</ref> believed that marks on a bone baton ({{Circa|25,000 BC}}) represented a lunar calendar. Other marked bones may also represent lunar calendars. Similarly, Michael Rappenglueck believes that marks on a 15,000-year-old cave painting represent a lunar calendar.<ref>{{cite news |url= | Alexander Marshack, in a controversial reading,<ref>James Elkins, ''[https://books.google.com/books?id=5Ku6YdWurMgC&pg=PA63&lpg=PA63 Our beautiful, dry, and distant texts]'' (1998) 63ff.</ref> believed that marks on a bone baton ({{Circa|25,000 BC}}) represented a lunar calendar. Other marked bones may also represent lunar calendars. Similarly, Michael Rappenglueck believes that marks on a 15,000-year-old cave painting represent a lunar calendar.<ref>{{cite news |url=https://news.bbc.co.uk/2/hi/science/nature/975360.stm |title=Oldest lunar calendar identified |work=BBC News |date=16 October 2000 |access-date=14 March 2013 |archive-date=11 February 2021 |archive-url=https://web.archive.org/web/20210211233146/http://news.bbc.co.uk/2/hi/science/nature/975360.stm |url-status=live }}</ref> | ||
===Lunisolar=== | ===Lunisolar=== | ||
| Line 96: | Line 97: | ||
===Arithmetical and astronomical=== | ===Arithmetical and astronomical=== | ||
[[File:JudischerKalender-1831 ubt.jpeg|thumb|Calendar of the [[Qahal]], 5591 (1831)]] | [[File:JudischerKalender-1831 ubt.jpeg|thumb|Calendar of the [[Qahal]], [[Anno Mundi|AM]] 5591 (1831 [[Common Era|CE]])]] | ||
An ''astronomical calendar'' is based on ongoing observation; examples are the religious Islamic calendar and the old religious Jewish calendar in the time of the [[Second Temple]]. Such a calendar is also referred to as an ''observation-based'' calendar. The advantage of such a calendar is that it is perfectly and perpetually accurate. The disadvantage is that working out when a particular date would occur is difficult. | An ''astronomical calendar'' is based on ongoing observation; examples are the religious Islamic calendar and the old religious Jewish calendar in the time of the [[Second Temple]]. Such a calendar is also referred to as an ''observation-based'' calendar. The advantage of such a calendar is that it is perfectly and perpetually accurate. The disadvantage is that working out when a particular date would occur is difficult. | ||
| Line 103: | Line 104: | ||
===Other variants=== | ===Other variants=== | ||
The early [[Roman calendar]], created during the reign of [[Romulus]], lumped the 61 days of the winter period together as simply "winter".<ref>{{Cite web |last=Jones |first=Derek |date=2018 | The early [[Roman calendar]], created during the reign of [[Romulus]], lumped the 61 days of the winter period together as simply "winter".<ref>{{Cite web |last=Jones |first=Derek |date=8 March 2018 |title=Roman Calendar |url=https://editions.covecollective.org/chronologies/roman-calendar |access-date=18 March 2024 |website=editions.covecollective.org |language=en}}</ref> Over time, this period became January and February; through further changes over time (including the creation of the [[Julian calendar]]) this calendar became the modern Gregorian calendar, introduced in the 1570s.<ref>{{Cite magazine |date=29 December 2023 |title=Who Decided January 1st Is the New Year? |url=https://time.com/6550127/new-year-celebration-january-calendar-date-history/ |access-date=18 March 2024 |magazine=TIME |language=en}}</ref><ref>{{Cite web |last=Kelechava |first=Brad |date=11 February 2016 |title=History of the Standard Gregorian Calendar |url=https://blog.ansi.org/2016/02/history-of-standard-gregorian-calendar/ |access-date=18 March 2024 |website=The ANSI Blog |language=en-US}}</ref> | ||
==Usage== | ==Usage== | ||
[[File:World calendars map.svg|thumb|center | [[File:World calendars map.svg|thumb|center|Current usage of civil calendars in the world. Some countries use an additional calendar not listed here that determine holidays and other traditions, for example the [[Chinese calendar|Chinese]] or [[Islamic calendar|Islamic]] calendars.]] | ||
The primary practical use of a calendar is to identify days: to be informed about or to agree on a future event and to record an event that has happened. Days may be significant for agricultural, civil, religious, or social reasons. For example, a calendar provides a way to determine when to start planting or harvesting, which days are [[religious holiday|religious]] or [[civil holiday]]s, which days mark the beginning and end of business accounting periods, and which days have legal significance, such as the day taxes are due or a contract expires. Also, a calendar may, by identifying a day, provide other useful information about the day such as its season. | The primary practical use of a calendar is to identify days: to be informed about or to agree on a future event and to record an event that has happened. Days may be significant for agricultural, civil, religious, or social reasons. For example, a calendar provides a way to determine when to start planting or harvesting, which days are [[religious holiday|religious]] or [[civil holiday]]s, which days mark the beginning and end of business accounting periods, and which days have legal significance, such as the day taxes are due or a contract expires. Also, a calendar may, by identifying a day, provide other useful information about the day such as its season. | ||
| Line 112: | Line 113: | ||
===Gregorian=== | ===Gregorian=== | ||
{{Calendar|lk=on|show_year=on|float=right|month=current}} | |||
The [[Gregorian calendar]] is the ''[[de facto]]'' international standard and is used almost everywhere in the world for civil purposes. The widely used solar aspect is a cycle of leap days in a 400-year cycle designed to keep the duration of the year aligned with the [[solar year]].{{sfn | Blackburn | Holford-Strevens | 2003 | pp = 682–683}} There is a lunar aspect which approximates the position of the moon during the year, and is used in the [[Computus|calculation of the date of Easter]].{{sfn | Blackburn | Holford-Strevens | 2003 | pp = 817–820}} Each Gregorian year has either 365 or 366 days (the leap day being inserted as 29 February), amounting to an average Gregorian year of 365.2425 days (compared to a solar year of 365.2422 days).{{sfn | Dershowitz | Reingold | 2008 | pp = 47, 187}} | The [[Gregorian calendar]] is the ''[[de facto]]'' international standard and is used almost everywhere in the world for civil purposes. The widely used solar aspect is a cycle of leap days in a 400-year cycle designed to keep the duration of the year aligned with the [[solar year]].{{sfn | Blackburn | Holford-Strevens | 2003 | pp = 682–683}} There is a lunar aspect which approximates the position of the moon during the year, and is used in the [[Computus|calculation of the date of Easter]].{{sfn | Blackburn | Holford-Strevens | 2003 | pp = 817–820}} Each Gregorian year has either 365 or 366 days (the leap day being inserted as 29 February), amounting to an average Gregorian year of 365.2425 days (compared to a solar year of 365.2422 days).{{sfn | Dershowitz | Reingold | 2008 | pp = 47, 187}} | ||
| Line 122: | Line 124: | ||
The most important use of pre-modern calendars is keeping track of the [[liturgical year]] and the observation of religious feast days. | The most important use of pre-modern calendars is keeping track of the [[liturgical year]] and the observation of religious feast days. | ||
While the Gregorian calendar is itself historically motivated to the calculation of the [[Easter date]], it is now in worldwide secular use as the ''de facto'' standard. Alongside the use of the Gregorian calendar for secular matters, there remain several calendars in use for religious purposes. | While the Gregorian calendar is itself historically motivated to the calculation of the [[Easter date]], it is now in worldwide secular use<ref>{{Cite news |title=Calendar {{!}} Chronology, History, & Types {{!}} Britannica |url=https://www.britannica.com/science/calendar |archive-url=http://web.archive.org/web/20260311002524/https://www.britannica.com/science/calendar |archive-date=2026-03-11 |access-date=2026-03-13 |work=Encyclopedia Britannica |language=en}}</ref> as the ''de facto'' standard. Alongside the use of the Gregorian calendar for secular matters, there remain several calendars in use for religious purposes. | ||
Western Christian liturgical calendars are based on the cycle of the Roman Rite of the Catholic Church, and generally include the liturgical seasons of [[Advent]], [[Christmas]], Ordinary Time (Time after [[Epiphany (holiday)|Epiphany]]), [[Lent]], [[Easter]], and Ordinary Time (Time after [[Pentecost]]). Some Christian calendars do not include Ordinary Time and every day falls into a denominated season. | Western Christian liturgical calendars are based on the cycle of the Roman Rite of the Catholic Church, and generally include the liturgical seasons of [[Advent]], [[Christmas]], Ordinary Time (Time after [[Epiphany (holiday)|Epiphany]]), [[Lent]], [[Easter]], and Ordinary Time (Time after [[Pentecost]]). Some Christian calendars do not include Ordinary Time and every day falls into a denominated season. | ||
The [[Eastern Orthodox Church]] employs the use of 2 liturgical calendars; the [[Julian calendar]] (often called the Old Calendar) and the [[Revised Julian calendar|Revised Julian Calendar]] (often called the New Calendar). The Revised Julian Calendar is nearly the same as the Gregorian calendar, with the addition that years divisible by 100 are not [[leap years]], except that years with remainders of 200 or 600 when divided by 900 remain leap years, e.g. 2000 and 2400 as in the Gregorian calendar.<ref>{{Cite web |title=The Revised Julian Calendar |url=https://www.timeanddate.com/calendar/revised-julian-calendar.html |access-date=2024 | The [[Eastern Orthodox Church]] employs the use of 2 liturgical calendars; the [[Julian calendar]] (often called the Old Calendar) and the [[Revised Julian calendar|Revised Julian Calendar]] (often called the New Calendar). The Revised Julian Calendar is nearly the same as the Gregorian calendar, with the addition that years divisible by 100 are not [[leap years]], except that years with remainders of 200 or 600 when divided by 900 remain leap years, e.g. 2000 and 2400 as in the Gregorian calendar.<ref>{{Cite web |title=The Revised Julian Calendar |url=https://www.timeanddate.com/calendar/revised-julian-calendar.html |access-date=5 June 2024 |website=www.timeanddate.com |language=en}}</ref>{{discuss}} | ||
The [[Islamic calendar]] or Hijri calendar is a [[lunar calendar]] consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in most of the Muslim countries (concurrently with the Gregorian calendar) and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. Its epoch is the [[Anno Hegirae|Hijra]] (corresponding to AD 622). With an annual drift of 11 or 12 days, the seasonal relation is repeated approximately every 33 Islamic years. | The [[Islamic calendar]] or Hijri calendar is a [[lunar calendar]] consisting of 12 lunar months in a year of 354 or 355 days. It is used to date events in most of the Muslim countries (concurrently with the Gregorian calendar) and used by Muslims everywhere to determine the proper day on which to celebrate Islamic holy days and festivals. Its epoch is the [[Anno Hegirae|Hijra]] (corresponding to AD 622). With an annual drift of 11 or 12 days, the seasonal relation is repeated approximately every 33 Islamic years. | ||
| Line 136: | Line 138: | ||
Most of the Hindu calendars are inherited from a system first enunciated in [[Vedanga Jyotisha]] of Lagadha, standardized in the ''[[Surya Siddhanta|Sūrya Siddhānta]]'' and subsequently reformed by astronomers such as [[Aryabhata|Āryabhaṭa]] (AD 499), [[Varahamihira|Varāhamihira]] (6th century) and [[Bhāskara II]] (12th century). | Most of the Hindu calendars are inherited from a system first enunciated in [[Vedanga Jyotisha]] of Lagadha, standardized in the ''[[Surya Siddhanta|Sūrya Siddhānta]]'' and subsequently reformed by astronomers such as [[Aryabhata|Āryabhaṭa]] (AD 499), [[Varahamihira|Varāhamihira]] (6th century) and [[Bhāskara II]] (12th century). | ||
The [[Hebrew calendar]] is used by [[Jews]] worldwide for religious and cultural affairs, also influences civil matters in Israel (such as [[public holiday|national holidays]]) and can be used business dealings (such as for the dating of [[cheque]]s).<ref>{{Cite web |title=About the Hebrew Calendar {{!}} Yale University Library |url=https://web.library.yale.edu/cataloging/hebraica/about-hebrew-calendar |access-date=2024 | The [[Hebrew calendar]] is used by [[Jews]] worldwide for religious and cultural affairs, also influences civil matters in Israel (such as [[public holiday|national holidays]]) and can be used in business dealings (such as for the dating of [[cheque]]s).<ref>{{Cite web |title=About the Hebrew Calendar {{!}} Yale University Library |url=https://web.library.yale.edu/cataloging/hebraica/about-hebrew-calendar |access-date=18 March 2024 |website=web.library.yale.edu}}</ref> | ||
Followers of the [[Baháʼí Faith]] use the [[Baháʼí calendar]]. The Baháʼí Calendar, also known as the Badi Calendar was first established by the Bab in the Kitab-i-Asma. The Baháʼí Calendar is also purely a solar calendar and comprises 19 months each having nineteen days. | Followers of the [[Baháʼí Faith]] use the [[Baháʼí calendar]]. The Baháʼí Calendar, also known as the Badi Calendar was first established by the Bab in the Kitab-i-Asma. The Baháʼí Calendar is also purely a solar calendar and comprises 19 months each having nineteen days. | ||
| Line 147: | Line 149: | ||
===Fiscal=== | ===Fiscal=== | ||
{{Main|Fiscal calendar}} | {{Main|Fiscal calendar}} | ||
[[File:Pieter Brueghel the Younger (or workshop) The Payment of the Tithes Bonhams.jpg|thumb|''The Payment of the Tithes'' (The tax-collector), also known as ''Village Lawyer'', by [[Pieter Brueghel the Younger]] ]] | [[File:Pieter Brueghel the Younger (or workshop) The Payment of the Tithes Bonhams.jpg|thumb|''The Payment of the Tithes'' (The tax-collector), also known as ''Village Lawyer'', by [[Pieter Brueghel the Younger]] ]] | ||
| Line 154: | Line 157: | ||
==Formats== | ==Formats== | ||
[[File:Petaluma and Santa Rosa Railroad Co. Calendar.jpg|thumb|A calendar from the [[Petaluma and Santa Rosa Railroad]]|308x308px]] | |||
[[File:Petaluma and Santa Rosa Railroad Co. Calendar.jpg|thumb|A calendar from the [[Petaluma and Santa Rosa Railroad]]]] | |||
The term ''calendar'' applies not only to a given scheme of timekeeping but also to a specific record or device displaying such a scheme, for example, an [[appointment book]] in the form of a pocket calendar (or [[personal organizer]]), desktop calendar, a [[wall calendar]], etc. | The term ''calendar'' applies not only to a given scheme of timekeeping but also to a specific record or device displaying such a scheme, for example, an [[appointment book]] in the form of a pocket calendar (or [[personal organizer]]), desktop calendar, a [[wall calendar]], etc. | ||
In a paper calendar, one or two sheets can show a single day, a week, a month, or a year. If a sheet is for a single day, it easily shows the date and the weekday. If a sheet is for multiple days it shows a conversion table to convert from weekday to date and back. With a special pointing device, or by crossing out past days, it may indicate the current date and weekday. This is the most common usage of the word. | In a paper calendar, one or two sheets can show a single day, a week, a month, or a year. If a sheet is for a single day, it easily shows the date and the weekday. If a sheet is for multiple days it shows a conversion table to convert from weekday to date and back. With a special pointing device, or by crossing out past days, it may indicate the current date and weekday. This is the most common usage of the word. | ||
[[File:Mechanische muurkalender van het merk Star - INDUS V09604.JPG|thumb|219x219px|Mechanical wall calendar in bakelite (collection Museum of Industry Ghent)]] | |||
In the | In modern Gregorian calendar displays, the order of the weekdays is determined by local convention rather than by the Gregorian calendar itself. In the [[United States]], calendars commonly place [[Sunday]] in the first column and [[Saturday]] in the last. By contrast, the ISO 8601 standard defines [[Monday]] as the first day of the week, and Monday-first layouts are widely used in [[Europe]], including in the [[United Kingdom]].<ref>{{cite web|title=Format dates and times|url=https://learn.microsoft.com/en-us/globalization/locale/date-time-formats|website=Microsoft Learn|date=2023-07-20|access-date=2026-04-05}}</ref><ref>{{cite web|title=Unicode Locale Data Markup Language (LDML), Part 4: Dates|url=https://unicode-org.github.io/cldr/ldml/tr35-dates.html|website=Unicode Consortium|access-date=2026-04-05}}</ref><ref>{{cite web |title=7 Days of the Week|url=https://www.timeanddate.com/calendar/days/|website=timeanddate.com|access-date=2026-04-05}}</ref> | ||
Gregorian calendars are most commonly presented in monthly grids with seven columns, one for each day of the week, and up to six rows for the days of the month, depending on the month’s length and the weekday on which it begins.<ref>{{cite web |last=Petzold |first=Charles|title=Customizing the New WPF Calendar Controls|url= https://learn.microsoft.com/en-us/archive/msdn-magazine/2009/june/customizing-the-new-wpf-calendar-controls|website=Microsoft Learn|date=June 2009|access-date=2026-04-05}}</ref> For uses organized around weeks rather than months, many calendaring systems also provide dedicated week views instead of month-by-month grids.<ref>{{cite web |title=Calendar views |url=https://help.hcl-software.com/dom_designer/9.0.1/appdev/H_ABOUT_CALENDAR_VIEWS_ABOUT.html|website=HCL Software Product Documentation|access-date=2026-04-05}}</ref> | |||
==Software== | ==Software== | ||
{{Main|Calendaring software}} | {{Main|Calendaring software}} | ||
{{Further|:Category:Calendaring standards}} | {{Further|:Category:Calendaring standards}} | ||
Calendaring software provides users with an electronic version of a calendar, and may additionally provide an appointment book, address book, or contact list. | Calendaring software provides users with an electronic version of a calendar, and may additionally provide an appointment book, address book, or contact list. | ||
Calendaring is a standard feature of many [[Personal digital assistant|PDAs]], [[Enterprise digital assistant|EDAs]], and [[smartphones]]. The software may be a local package designed for individual use (e.g., [[Lightning (software)|Lightning]] extension for [[Mozilla Thunderbird]], [[Microsoft Outlook]] without Exchange Server, or [[Windows Calendar]]) or maybe a networked package that allows for the sharing of information between users (e.g., [[Mozilla Sunbird]], [[Windows Live Calendar]], [[Google Calendar]], or [[Microsoft Outlook]] with Exchange Server). | Calendaring is a standard feature of many [[Personal digital assistant|PDAs]], [[Enterprise digital assistant|EDAs]], and [[smartphones]]. The software may be a local package designed for individual use (e.g., [[Lightning (software)|Lightning]] extension for [[Mozilla Thunderbird]], [[Microsoft Outlook]] without Exchange Server, or [[Windows Calendar]]) or maybe a networked package that allows for the sharing of information between users (e.g., [[Mozilla Sunbird]], [[Windows Live Calendar]], [[Google Calendar]], or [[Microsoft Outlook]] with Exchange Server). | ||
In addition to displaying dates and maintaining contacts, calendaring software is commonly used to create and manage events, tasks, recurring appointments, reminders, and availability information such as free/busy time.<ref>{{cite web |title=RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar) |url=https://www.rfc-editor.org/rfc/rfc5545.html|website=RFC Editor|date=September 2009|access-date=2026-04-05}}</ref> | |||
For interoperability, many calendar applications import and export data in the [[iCalendar]] format, often using the ''.ics'' filename extension. The iCalendar specification defines calendar components such as events, to-dos, journal entries, time zone data, and free/busy information independently of any single service or platform.<ref>{{cite web |title=RFC 5545: Internet Calendaring and Scheduling Core Object Specification (iCalendar) |url=https://www.rfc-editor.org/rfc/rfc5545.html|website=RFC Editor|date=September 2009|access-date=2026-04-05}}</ref> | |||
Networked calendaring systems often use [[CalDAV]], an extension of [[WebDAV]], to access, manage, and share calendar data stored on a remote server.<ref>{{cite web |title=RFC 4791: Calendaring Extensions to WebDAV (CalDAV) |url=https://www.rfc-editor.org/rfc/rfc4791.html |website=RFC Editor |date=March 2007 |access-date=2026-04-05}}</ref> Scheduling between users may also rely on the iCalendar Transport-Independent Interoperability Protocol (iTIP), while email-based invitations and replies are commonly carried using iMIP over Internet mail.<ref>{{cite web |title=RFC 5546: iCalendar Transport-Independent Interoperability Protocol (iTIP) |url=https://www.rfc-editor.org/rfc/rfc5546.html |website=RFC Editor |date=December 2009 |access-date=2026-04-05}}</ref><ref>{{cite web |title=RFC 6047: iCalendar Message-Based Interoperability Protocol (iMIP) |url=https://www.rfc-editor.org/rfc/rfc6047.html|website=RFC Editor|date=December 2010|access-date=2026-04-05}}</ref> | |||
Later extensions to iCalendar added richer event-publishing metadata, improved alarm handling, and additional ways to express relationships between calendar components.<ref>{{cite web |title=RFC 9073: Event Publishing Extensions to iCalendar |url=https://www.rfc-editor.org/rfc/rfc9073.html |website=RFC Editor |date=August 2021 |access-date=2026-04-05}}</ref><ref>{{cite web |title=RFC 9074: "VALARM" Extensions for iCalendar |url=https://www.rfc-editor.org/rfc/rfc9074.html |website=RFC Editor |date=August 2021 |access-date=2026-04-05}}</ref><ref>{{cite web |title=RFC 9253: Support for iCalendar Relationships|url=https://www.rfc-editor.org/rfc/rfc9253.html |website=RFC Editor|date=June 2022|access-date=2026-04-05}}</ref> | |||
== See also == | == See also == | ||
{{div col}} | {{div col}} | ||
* | * {{anl|Advent calendar}} | ||
* {{anl|Calendar reform}} | |||
* {{anl|Calendrical calculation}} | |||
* {{anl|General Roman Calendar}} | |||
* [[History of calendars]] | |||
* {{anl|Horology}} | |||
* [[List of calendars]] | * [[List of calendars]] | ||
* [[List of international common standards]] | * [[List of international common standards]] | ||
* [[List of unofficial observances by date]] | * [[List of unofficial observances by date]] | ||
* | * {{anl|Real-time clock}}. Underlies the Calendar software on modern computers. | ||
* | * {{anl|Sabbath}} | ||
* {{anl|Unit of time}} | |||
{{div col end}} | {{div col end}} | ||