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.
Modern day Indonesian Gregorian calendar for a Catholic church
British calendar, 1851, gilt bronze and malachite, height: 20.3 cm, Metropolitan Museum of Art (New York City)
Equinox seen from the astronomic calendar of Pizzo Vento at Fondachelli Fantina, Sicily
Catalan early 20th century perpetual calendar
A day is the time period of a full rotation of the Earth with respect to the Sun. On average, this is 24 hours. As a day passes at a given location it experiences morning, noon, afternoon, evening, and night. This daily cycle drives circadian rhythms in many organisms, which are vital to many life processes.
Decimal clock face, made in around the start of the 19th century
Night in art
Image: Midtown Manhattan from Weehawken September 2021 panorama 1
Image: Midtown Manhattan from Weehawken September 2021 panorama 2
