Calendar
A calendar is a system of organizing days.1 This is done by giving names to periods of time, typically days, weeks, months and years.123 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.4 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 sun or the moon.567 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.
Printed 2026-06-28.
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Footnotes
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“Calendars and their History”. eclipse.gsfc.nasa.gov. Retrieved 13 March 2026. ↩ ↩2
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Guo, Rongxing (16 May 2018). Human-Earth System Dynamics: Implications to Civilizations. Springer. p. 159. ISBN 978-981-13-0547-4. ↩
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Bond, Thomas; Hughes, Chris (3 December 2013). Singapore PSLE Mathematics Challenging Practice Solutions (Yellowreef). Yellowreef Limited. ISBN 978-0-7978-0222-3. ↩
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“CALENDAR definition and meaning | Collins English Dictionary”. www.collinsdictionary.com. 3 March 2026. Retrieved 13 March 2026. ↩
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“Do menstrual and lunar cycles synchronize? What scientists say”. www.medicalnewstoday.com. 12 February 2021. Retrieved 12 March 2024. ↩
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“Introduction to Calendars”. aa.usno.navy.mil. Retrieved 12 March 2024. ↩
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“History – Ancient Egyptian Calendar” (PDF). Archived from the original (PDF) on 12 March 2024. Retrieved 12 March 2024. ↩