Editing Roman calendar (section)

==Weeks==
[[File:Fasti Praenestini Massimo n2.jpg|thumb|A fragment of the ''[[Fasti Praenestini]]'' for the month of April (''[[Aprilis]]''), showing its nundinal letters on the left side]]
{{main|Nundinae|Planetary hours|Week}}
The [[nundinae]] were the market days which formed a kind of [[weekend]] in [[ancient Rome|Rome]], [[Roman Italy|Italy]], and some other parts of Roman territory. By Roman [[inclusive counting]], they were reckoned as "ninth days" although they actually occurred every eighth day. Because the republican and Julian years were not evenly divisible into eight-day periods, [[fasti|Roman calendars]] included a column giving every day of the year a [[nundinal letter]] from A to H marking its place in the cycle of market days. Each year, the letter used for the markets would shift {{nowrap|2–5 letters}} along the cycle. As a day when the city swelled with rural [[plebeians]], they were overseen by the [[aedile]]s and took on an important role in Roman legislation, which was supposed to be announced for three nundinal weeks (between {{nowrap|17 and 24 days}}) in advance of its coming to a vote. The [[patricians]] and their [[Patronage in ancient Rome|clients]] sometimes exploited this fact as a kind of [[filibuster]], since the [[tribunes of the plebs]] were required to wait another three-week period if their proposals could not receive a vote before dusk on the day they were introduced. Superstitions arose concerning the bad luck that followed a nundinae on the nones of a month or, later, on the [[January Kalends|first day]] of [[January (Roman month)|January]]. Intercalation was supposedly used to avoid such coincidences, even after the Julian reform of the calendar.

The [[7-day week]] began to be observed in [[Roman Italy|Italy]] in the early imperial period,{{sfnp|Brind'Amour|1983|pp=256–275}} as practitioners and converts to eastern religions introduced [[planetary hours|Hellenistic and Babylonian astrology]], the [[Judaism in ancient Rome|Jewish]] [[Saturday]] [[Jewish sabbath|sabbath]], and the [[Christianity in ancient Rome|Christian]] [[Lord's Day]]. The system was originally used for private worship and astrology but had replaced the nundinal week by the time [[Constantine I (emperor)|Constantine]] made [[Sunday]] (''{{lang|la|dies Solis}}'') an official day of rest in AD&nbsp;321. The hebdomadal week was also reckoned as a cycle of letters from A to G; these were adapted for Christian use as the [[dominical letter]]s.