Editing Planetary hours (section)

==History==
The astrological order of the days was explained by [[Vettius Valens]] and [[Dio Cassius]] (and [[Chaucer]] gave the same explanation in his ''[[Treatise on the Astrolabe]]''). According to these authors, it was a principle of astrology that the heavenly bodies presided, in succession, over the hours of the day. 
The [[Ptolemaic system#Geocentricty|Ptolemaic system]] of planetary spheres asserts that the order of the heavenly bodies, from the farthest to the closest to the Earth  is: [[Saturn]], [[Jupiter]], [[Mars]], [[Sun]], [[Venus]], [[Mercury (planet)|Mercury]], [[Moon]] (or, objectively, the planets are ordered from slowest to fastest moving as they appear in the night sky {{ndash}} note however that the sun, Venus, and Mercury all advance by 360° per year, on average).<ref>
{{cite journal
| last = Falk
| first = Michael
| title = Astronomical names for the days of the week
| journal = Journal of the Royal Astronomical Society of Canada
| volume = 93
| issue = 1999–06
| pages = 122–133
| date = 19 March 1999
| bibcode = 1999JRASC..93..122F
}}</ref>

In astrological theory, not only the days of the week, but the hours of the day are dominated by the seven luminaries. If the first hour of a day is dominated by Saturn ([[File:Saturn symbol (fixed width).svg|20px|class=skin-invert-image|Saturn]]), then the second hour is dominated by Jupiter ([[File:Jupiter symbol (fixed width).svg|20px|class=skin-invert-image|Jupiter]]), the third by Mars ([[File:Mars symbol (fixed width).svg|20px|class=skin-invert-image|Mars]]), and so on
with the Sun ([[File:Sun symbol (fixed width).svg|20px|class=skin-invert-image|Sun]]), Venus ([[File:Venus symbol (fixed width).svg|20px|class=skin-invert-image|Venus]]), Mercury ([[File:Mercury symbol (fixed width).svg|20px|class=skin-invert-image|Mercury]]), and the moon ([[File:Moon decrescent symbol (fixed width).svg|20px|class=skin-invert-image|Moon]]), so that the sequence of planets repeats every seven hours. Therefore, the twenty-fifth hour, which is the first hour of the following day, is dominated by the Sun; the forty-ninth hour, which is the first hour of the next day, by the Moon. Thus, if a day is labelled by the planet which dominates its first hour, then Saturn's day is followed by the Sun's day, which is followed by the Moon's day, and so forth, as shown below.

According to Vettius Valens, the first hour of the day began at sunset, which follows Greek and Babylonian convention. He also states that the light and dark halves of the day were presided over by the heavenly bodies of the first hour of each half. 
This is confirmed by a Pompeian graffito which calls 6 February 60 a "Sunday", even though by modern reckoning it would have been a Wednesday. Assuming that this graffito used the sunset naming convention of Valens, it would follow that 6 February 60 was a Wednesday according to the sunrise naming convention used in modern astrology, suggesting that there may be an unbroken continuity of weekdays connecting the modern period to the 1st century AD at least.<ref>''Nerone Caesare Augusto Cosso Lentuol Cossil fil. Cos. VIII idus Febr(u)arius dies solis, luna XIIIIX nun(dinae) Cumis, V (idus Februarias) nun(dinae) Pompeis''. Robert Hannah, [https://books.google.com/books?id=PeVLAQAAQBAJ&pg=PA89 "Time in Written Spaces"], in: Peter Keegan, Gareth Sears, Ray Laurence (eds.),  ''Written Space in the Latin West, 200 BC to AD 300'', A&C Black, 2013, p. 89.</ref>

These two overlapping naming systems continued to be used by [[Alexandria]]n Christians during the 4th century, but the days in both were simply numbered {{nowrap|1 to 7}}.<ref name=Festal>{{citation |translator-last=Burgess |translator-first=Henry |title=The Festal Epistles of S. Athanasius |url=https://archive.org/stream/38ALibraryOfFathersOfTheHolyCatholicV38#page/n23/mode/2up |series=A Library of Fathers of the Holy Catholic Church, anterior to the division of the East and West |year=1854 |pages=xv–xxvi}}</ref> Although names of planets (or the gods eponymous of the planets) were not used, the week beginning on Wednesday was named in [[Greek language|Greek]] τῶν θεῶν ''tṓn theṓn'' ([day] of the [planetary] gods), as used by the late 4th century editor of the 328–373 [[Easter]] letters of [[Athanasius of Alexandria|Bishop Athanasius]],<ref name=Festal/> and was named ''tentyon'' (a [[Ge'ez language|Ge'ez]] transcription of the Greek words) in a table of Easter dates for 311–369 that survives in an [[Ethiopian]] copy.<ref name=Ethiopic>{{citation |last=Neugebauer |first=Otto |title=Ethiopic Astronomy and Computus |url=https://books.google.com/books?id=7TW3DAEACAAJ |year=2016 |orig-year=First published 1979 by Austrian Academy of Sciences |publisher=Red Sea Press |pages=53–58, 94, 212–219 |isbn=978-1-56902-440-9}}</ref> The day of the week of {{nowrap|Thoth 1}} of the [[Alexandrian calendar]] and of {{nowrap|Maskaram 1}} of the [[Ethiopian calendar]], the first day of their respective years,<ref>Both of these first days of the year are {{nowrap|August 29}} in the [[Julian calendar]] for the day after the end of Alexandrian and Ethiopian common years and {{nowrap|August 30}} in those years after leap years having a sixth [[Intercalary month (Egypt)|epagomenal day]] the day before.</ref> is given using the ''ton theon'' and ''tentyon'' respectively, both weeks beginning {{nowrap|Wednesday {{=}} 1}} in a column of 532-year Paschal tables. In a neighboring column of those same tables, both first days are also given a day of the week called the ''Day of John'' with a week beginning {{nowrap|Sunday {{=}} 1}}. Both the ''ton theon'' and ''tentyon'' of these first days of the Alexandrian and Ethiopian years are numerically identical to the day of the week of the next {{nowrap|March 24}} in the [[Julian calendar]] using a {{nowrap|Sunday {{=}} 1}} week,<ref>March 24 = Thoth/Maskaram 208 {{nowrap|≡ Thoth/Maskaram 5 mod 7}}.</ref> which medieval computists called the ''concurrent''. These overlapping weeks are still used in the Ethiopian [[computus]].<ref  name=Ethiopic/>