When I was taking Japanese, I was struck by how similar our day names were to theirs. 日曜日 -- nichiyoubi -- Sun Day. 月曜日 -- getsuyoubi -- Moon Day. It wasn't a coincidence. Japan adopted its version of the Western calendar during the Meiji Restoration, as it adopted so many Western customs. Thankfully, they discarded the Norse pantheon for the other days in favor of elemental names, with gold (or money) reserved for Friday.
My first pass at this centered the week around the weekend, with the weekdays named according to their proximity to the weekend. We have this in English already with Wednesday, which we call "Hump Day" -- halfway to the weekend! Over the hump!
A shortcoming common both to the traditional English day names, and my first pass, was non-unique initial letters. In practice, this makes us have to distinguish Tuesday (T) from Thursday (Th) and Saturday (S) from Sunday (Su).
My first pass also preserved the weekend day names, but that preserved the pagan names for those two days, so they had to go. Now replaced by ordinal names for their position in the week.
Here's the list of changes.
1. Sunday (Sun Day) => Firstday (F)
2. Monday (Moon Day) => Recovery Day => Recday (R)
3. Tuesday (Tyr's Day) => Thin(g)day (T)
4. Wednesday (Wotan's Day) => Hum(p)day (H)
5. Thursday (Thor's Day) => Penultiday => Penday (P)
6. Friday (Freia's Day) => preSaturday => Anteday (A)
7. Saturday (Satyr's Day) => Sevenday (S)
Sunday is the first day of the week, and is now called Firstday. Monday is the day you recover from the weekend. Recovery Day is too long, so I shortened it to Recday.
Tuesday becomes Thingday, which is actually the literal translation of the German word for Tuesday, Dienstag. An online etymology suggests an origin from the god Thingus, a possible alternate name for Tyr. We're just going to go with "Thing" in its modern meaning, a day for miscellany. It's hard to say "Thingday" without a pause because of the hard 'g', so popular pronunciation will soften or omit the 'g' sound, making it homophonous with "Thinday".
Wednesday already had "Hump Day", and we preserve that here. Since, again, the hard 'p' sound doesn't flow well, so the 'p' is omitted to make it homophonous with "Humday". It's midweek, things are humming along, the weekend is on its way.
The first version of this project renamed "Thursday" to be the penultimate (second to last) day in the work week, or "Penultiday". I really liked that, and used it every time I could, but in the interest of making the new weekday names flow, I shorten it here in this second revision to "Penday". Maybe a day to write letters to friends?
The first version of this project had Friday as "preSaturday", but combined with "Penultiday" and "Postsunday" (AKA Monday), that was three days that started with the letter "P". I rename it here as "Anteday", the "before" day.
Saturday becomes Sevenday, matching up with Firstday on the other side. It's the seventh day, time for a rest.
As a child, I had a speech impediment, and could not pronounce the soft "th" sound, so "Thursday" sounded pretty much like "Firstday". Now Firstday is a day. Take that, haters. Unfortunately, future kids with the same speech difficulty will call Thingday "Finday", but I think that's endearing, personally.
Enjoy your new day names!