Actually, a lunar cycle is just about 29.5 days long, not 28, which makes lunar calendars even more interesting. Seven is still a good divisor for 29.5…or at least it’s as good as any whole number is going to be.
Western calendar months, by the way, are just about four and a half weeks long, except of course for February. Nobody loves February.
Urdu
Sunday: Itwar
Monday: Peer
Tuesday: Mangel
Wednesday: Budh
Thurday: Jumay-Raat
Friday: Juma
Saturday: Hafta
And despite what dopers who think in Streotypes may assume, Pakistans weekend is Sunday… only.
Some of the day names do have some significance, Friday is named after Juma prayers, Thursday is called “Juma-Raat”, literally “Friday Night” or the night before Friday, and Saturday is “hafta” which is the same word for week, fitting as it is the end of the week.
According to Wikipedia, the Hindu day-names come from a text called the Yavanajataka which was translated from Greek in 150 CE, so it seems it is not a coincidence.
Again, according to wikpedia, the seven day week was used in India at least as far back as the first century BCE.
And the Greeks conqured and had settlements in parts of what is now Pakistan at least 300 years before.
The article actually just says they’re the same ones as used in Europe, not that it was imported from there, which would be odd, since I don’t think there was any contact between the two places in 800 A.D. Presumably they inherited the system from one of the closer cultures mentioned above that used the same system.
Basque would like to throw a monkey wrench in your works.
Monday - astelehen “first of the week”
Tuesday - astearte “middle of the week”
Wednesday - asteasken “end of the week”
Thursday - ostegun “sky day”
Friday - ostiral (not sure here)
Saturday - larunbat “one week”
Sunday - igande (again not sure, but may have connections with the word for “ascension”)
There is some argument - don’t know if it’s backed up by firmer evidence than the names for Monday through Wednesday - that the Basque week originally had three days. But in any case there’s no deep, direct connection with elements, planets, or deities here.
In Hebrew, Sunday through Friday are just “First Day,” “Second Day…” “Sixth Day.”
Saturday is “Shabbat” – literally “He rested,” that is, the day on which God supposedly rested after creating the world in six days. Note that the name “Sabbath” and all it’s derivatives in European languages come from the word “Shabbat.”
Same as Korean. Also the characters for fire, water, wood, gold, and earth are the same characters we use for Mars, Mercury, Jupiter, Venus, and Saturn. Same in Thailand, it seems like.
The Swedish name for Saturday - lördag - is a modern version of the old Swedish word *løghardagher *and means “bath day”. It’s the same thing in Norwegian (lørdag/laurdag), Danish (lørdag), Icelandic (laugardagur) and Faroese (leygardagur).
All the other days we reserve for celestial bodies and deities, but Saturday is bath time, dammit. 
Correct. There was not any direct contact between Japan and Europe at the time.
Note from the article,
I’m going to guess that without a Sabboth or a similar offical weekly day of rest there wasn’t a real need for days of the week. I’ve heard (no cite) that there were more summer festivals “back then” which would compensate for not having a weekly day off.
In Portugues the week begins on Sunday, Domingo, with the rest of the days being called “second day…” (secunda-feira…) in order, until Satuday which is Sábado.
And candy time!
That seems very odd to me given the level of contact between Europe and Japan at that time. Mapping Time says that the Roman system “had diffused” to India by the second century A.D., and a Rome > India > China > Japan route makes more sense. He also suggests a complex Latin formula for the tying the hours of the day to the planets, and naming the day after whichever was ascendant in the morning, which would explain why Sun-Moon-Mars-Mercury-Jove-Venus-Saturn occurs in that order and not Sun-Mercury-Venus-Mars-Moon-Jove-Saturn.
Basque seems to like doing that in general.
Which is why it rules.
Except that latter order makes no sense unless you are aware of the order of the planets in a heliocentric system, knowledge that wasn’t available when the days of the week were set.