A week is a time unit equal to seven days. It is the standard time period used for cycles of rest days in most parts of the world, mostly alongside—although not strictly part of—the Gregorian calendar.
The days of the week were named after the classical planets (derived from the astrological system of planetary hours) in the Roman era. In English, the names are Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday.
ISO 8601 includes the ISO week date system, a numbering system for weeks within a given year – each week begins on a Monday and is associated with the year that contains that week's Thursday (so that if a year starts in a long weekend Friday–Sunday, week number one of the year will start after that). ISO 8601 assigns numbers to the days of the week, running from 1 to 7 for Monday through to Sunday.
The term "week" is sometimes expanded to refer to other time units comprising a few days, such as the nundinal cycle of the ancient Roman calendar or the "work week" or "school week" referring only to the days spent on those activities.
The Beatles - Eights days a week
Monday is the day of the week between Sunday and Tuesday. According to the international standard ISO 8601 it is the first day of the week. The name of Monday is derived from Old English Mōnandæg and Middle English Monenday, originally a translation of Latin dies lunae "day of the Moon".
Beethoven piano sonata 14, Moonlight Sonata, Kempff
Tuesday is a day of the week occurring after Monday and before Wednesday. According to some commonly used calendars (esp. in the US), it is the third day of the week. According to international standard ISO 8601, however, it is the second day of the week. The English name is derived from Old English Tiwesdæg and Middle English Tewesday, meaning "Tīw's Day", the day of Tiw or Týr, the god of single combat, victory and heroic glory in Norse mythology. Tiw was equated with Mars in the interpretatio germanica, and the name of the day is a translation of Latin dies Martis.
Melanie Safka - Ruby Tuesday
Wednesday (IPA: /ˈwɛnzdeɪ/) is the day of the week following Tuesday and before Thursday. According to international standard ISO 8601 adopted in most western countries it is the third day of the week. In countries that use the Sunday-first convention Wednesday is defined as the fourth day of the week. It is the fourth day of the week in the Judeo-Christian Hebrew calendar as well, which may have been adopted from the ancient Babylonian calendar. The name is derived from Old English Wōdnesdæg and Middle EnglishWednesdei, "day of Woden", reflecting the pre-Christian religion practiced by the Anglo-Saxons. In other languages, such as the French mercredi, the day's name is a calque of dies Mercurii "day of Mercury". It has the most letters out of all the Gregorian calendar days.
Wednesday is in the middle of the common Western five-day workweek that starts on Monday and finishes on Friday.
Simon and Garfunkel - Wednesday Morning
Thursday is the day of the week following Wednesday and before Friday. According to the ISO 8601 international standard adopted in most western countries, it is the fourth day of the week. In countries that use the Sunday-first convention, Thursday is defined as the fifth day of the week. It is the fifth day of the week in the Judeo-Christian liturgical calendar. It is often abbreviated to Th or Thu.
The name is derived from Old English Þūnresdæg and Middle English Thuresday (with loss of -n-, first in northern dialects, from influence of Old Norse Þorsdagr) meaning "Thor's Day". It was named after the Norse god of Thunder, Thor. Thunor, Donar (German, Donnerstag) and Thor are derived from the name of the Germanic god of thunder, Thunraz, equivalent to Jupiter in the interpretatio romana.
Pet Shop Boys - Thursday
Friday is the day after Thursday and the day before Saturday. In countries adopting Monday-first conventions as recommended by the international standard ISO 8601, it is the fifth day of the week. In countries that adopt a Sunday-first convention, it is the sixth day of the week. In other countries, Friday is the first day of the week-end, with Saturday the second. In Afghanistan and Iran, Friday is the last day of the week-end, with Saturday as the first day of the working week. Bahrain, the United Arab Emirates (U.A.E.) and Kuwait also followed this convention until they changed to a Friday–Saturday week-end, on September first, 2006 in Bahrain and the U.A.E., and a year later in Kuwait.In Iran, Friday is the only week-end day. In Saudi Arabia and the Maldives, there are two week-ends where Friday is the first week-end of the week while Saturday is the second week-end.
The name Friday comes from the Old English Frīġedæġ, meaning the "day of Frige", a result of an old convention associating the Old English goddess Frigg with the Roman goddess Venus, with whom the day is associated in many different cultures. The same holds for Frīatag in Old High German, Freitag in Modern German, and vrijdag in Dutch.
The Easy Beats - Friday on my mind
Saturday is the day of the week following Friday and preceding Sunday. The Romans named Saturday Sāturni diēs ("Saturn's Day") no later than the 2nd century for the planet Saturn, which controlled the first hour of that day, according to Vettius Valens.The day's name was introduced into West Germanic languages and is recorded in the Low German languages such as Middle Low Germansater(s)dach, Middle Dutch saterdag (Modern Dutch zaterdag) and Old English Sætern(es)dæġ and Sæterdæġ.However, the name was selected as a calque of the god Saturn, after whom the planet was named. The day was also referred to as "Sæternes dæġe" in an Old English translation of Bede's Ecclesiastical History of the English People. In Old English, Saturday was also known as sunnanæfen ("sun" + "eve" cf. dialectal German Sonnabend).
Bee Gees - Saturday Night Fever
For most Christians, Sunday is observed as a day of worship and rest, holding it as the Lord's Day and the day of Christ's resurrection. In some Muslim countries and Israel, Sunday is the first work day of the week. According to the Hebrew calendars and traditional Christian calendars, Sunday is the first day of the week. However, according to the International Organization for Standardization ISO 8601, Sunday is the seventh and last day of the week.https://en.wikipedia.org/wiki/Sunday - cite_note-2
Sunday, being the day of the Sun, as the name of the first day of the week, is derived from Hellenistic astrology, where the seven planets, known in English as Saturn, Jupiter, Mars, the Sun, Venus, Mercury and the Moon, each had an hour of the day assigned to them, and the planet which was regent during the first hour of any day of the week gave its name to that day. During the 1st and 2nd century, the week of seven days was introduced into Rome from Egypt, and the Roman names of the planets were given to each successive day.
U2 - Sunday, Bloody Sunday