A moment (momentum) was a medieval unit of time. The movement of a shadow on a sundial covered 40 moments in a solar hour. An hour in this case means one twelfth of the period between sunrise and sunset. The length of a solar hour depended on the length of the day, which in turn varied with the season, so the length of a moment in modern seconds was not fixed, but on average, a moment corresponds to 90 seconds. A day was divided into 24 hours of both equal and unequal lengths, the former being called natural or equinoctial, and the latter artificial. The hour was divided into four puncta (quarter-hours), ten minuta, or 40 momenta.
The unit was used by medieval computists before the introduction of the mechanical clock and the base 60 system in the late 13th century. The unit would not have been used in everyday life. For medieval commoners the main marker of the passage of time was the call to prayer at intervals throughout the day.
The earliest reference we have to the moment is from the 8th century writings of the Venerable Bede, who describes the system as 1 hour = 4 points = 5 lunar points = 10 minutes = 15 parts = 40 moments. Bede was referenced five centuries later by both Bartholomeus Anglicus in his early encyclopedia De Proprietatibus Rerum (On the Properties of Things), as well as Roger Bacon, by which time the moment was further subdivided into 12 ounces of 47 atoms each, although no such divisions could ever have been used in observation with equipment in use at the time.
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.