If you could create an additional day of the week, what would you name it and why?

Funday. Exists between Saturday and Sunday.
- Makes sense - after you've recharged, but before you have to prepare mentally and physically for the next week.
  
  Exactly!
  Saturday is my day to get stuff done, and Sunday is just preparing for Monday. Hence: Funday.
  
  You recharge in one day?
- Work should be illegal on Funday.
  
  Funday? Capitalists will be having none of that!
- Didn’t this happen in the cartoon Doug?
  
  You've unlocked a memory (Doug) but not the specifics. So, maybe?
- Wow, it's really neat to read exactly my idea.
  Get out of my head! 😉
- I work a weird sche, 2 on, 2 off, 3 on and then the next week it flips. So every other week working friday-sunday, or I'm off those days.
  An the one hand I support this because 3 day weekends are fucking great and everyone should have them
  On the other hand, I have a feeling that would change my schedule to 2-2-4, and while 4 day weekends are even better than 3 days, I'd probably be stuck working 4 days in a row on my working weekends
- Given how things are these days, I fear this would be the day you'd be forced to go into work to make up for any wfh you do.

Threesday, coming straight after Twosday.
- In Portuguese is kind like that: Domingo 2a feira 3a feira 4a feira 5a feira 6a feira Sábado
  
  Cool, so loosely translated 1st day, 2nd day, 3rd day, 4th day, 5th day, Saturday, Sunday?? That is amazing, confusing maybe, but amazing!

Correct the record.

Sextidi. It's what the sixth day was called in the French Revolutionary Calendar's ten-day week. But to follow the example of the ~~Roman~~ Gregorian calendar month-naming scheme, it will of course be the eighth day of the week. Also it contains the word "sex" which I expect will lead to both a lot of snickering teenagers and a lot of accidentally censored weekdays.
- Sextidi? Spicy
- Sextidi? Je ne vois pas de problème

Bjornsday
It would fit the mostly Nordic naming scheme but still credit me as the creator.

I'd name it Someday just to mess up with people.

I'd bring back Logsday.
- This is the only correct answer; we had another day and it was taken from us.

"Hiddenday"
It would be a day locked away from everyone's consciousness until the day's arrival. You'd be expecting your normal 7 day week, and go to bed Sunday night. Then the day after Sunday you'd wake will full knowledge of Hiddenday and everything you've ever done on prior Hiddendays. You'd already have a plan and knowledge if you were choosing to go to work to earn extra money, if you'd be staying home resting just a bit more, or going out to spend time with friends or family. You'd go to sleep on Hiddenday night knowing you'd forget the specific details of what you did that day ( but that you'd have that knowledge back next Hiddenday in 7 days). You'd wake up Monday morning remembering yesterday was Sunday, but you'd have any knowledge you accumulated the hidden day prior. If you worked and are paid hourly, you'd see an extra 8 hours of pay on your payslip, and no one would ever question why there were more hours. You'd carry the same rested feeling you had going to sleep on Hiddenday night but not know exactly why. Your family would tell you how much they loved spending time with you this week, and you'd feel the same, but you couldn't put your finger on exactly which day that happened.
We'd all go to work on Monday thinking how wonderful it would be if there was a 8th day.
- So February 29!
  If we honored cyclical calendar - lunar calendar - rather than the antichrist calendar created by the false prophets of the false church created by the Nicean Council that excluded fifteen books from our collection of myths to further service to Mammon, at the cost of schisming ourselves from within ourselves and with the global population, these things wouldn't be necessary. They were not the first to do this, however. gesture brutally at neolithic history.
  
  I like your style

Daylast, primarily to screw up that stupid "Day ending in a y" joke.

Here's a fun take for you: in Japanese its 月曜日、火曜日、水曜日、木曜日、金曜日、土曜日、and 日曜日, which translates to basically moon day, fire day, water day, tree day, metal day, earth day, and sun day--- although it's really celestial bodies, the very same mentioned in another comment (e g. Mars is the fire star, Tuesday).
It's supposedly derived from Chinese, though they probably got it from Romen influence given similarities.
Anyway, the eighth day probably needs to be 天王曜日 (which is basically heavenly king day) or 海王曜日 (sea god day, aka Neptune) but I'm unsatisfied with that. Plus, honestly it's way cooler as an elemental theme so my vote is 電曜日, denyoubi or electricity day, in honor of Pikachu. That day would be super effective.

Also Tuesday, it comes after Friday except on even numbered years it's after odd numbered Mondays. On leap years it starts halfway through Wednesdays.

EATTHERICHDAY

Dayday, so it can be payday on dayday for the baybay

Fraterday. The day of togetherness and brother/sisterhood

In Denmark we have a saying: "When there's two Thursdays in a week", which is used when someone asks you something like "when can we have this thing?" or "when will you do that thing?" or "when will you give me a million dollars?"
So, Thursday.

"I'll come up with a better name later" day
(Aka: Procrastination Day)
Why? I'll explain the reasoning later.

Logsday, because meta

Âäáàāåã
There are no words that start with â in romanian, so why not add one in english

Greenday - its always a day off, but no one is allowed to operate heavy machinery.

The days of the week come from the Sun (Sunday), Moon (Monday), and classic 5 planets (Tuesday = Mars, Wednesday = Mercury, Thursday = Jupiter, Friday = Venus, Saturday = Saturn). This makes more sense in some other languages, for example Spanish: marte / martes, mercurio / miercoles. Saturn = Saturday though is almost obvious.
So if there were another day in the week, I have no choice but to either:
name it Earthday
name it after Uranus, the next discovered planet
This gives us precedent to create up to 10 days per week by including all 8 planets plus sun & moon.
- the days in english are from old norse, no?
  Sun's day
  Moon's day
  Tyr's day
  Wodin's day
  Thor's day
  Freyr's day
  Saturn's day (okay that ones roman)
  
  Yes but if I remember correctly, each of those Norse gods are correlated with the Roman gods who share names with planets, which is how you can draw a connection between the planets and weekdays for English. The same connection exists in many languages across the world including Spanish, French, Hindi, Japanese.

Calcday, other days of the week are named after gods, so I would add some scientific touch: Calculus day
- Sunday and Mo(o)nday are named after celestial bodies. Is astronomy not scientific enough for you?
  
  Fair point, then the new weekday should be called Jeday.
  
  The gods that the weekdays are named after also have associated planets, so really every day is named after a celestial body already.
  Ex: Saturday is obviously Saturn Day, Thursday is Thor's Day, with Thor being the equivalent of the Roman Jupiter, so Thursday is indirectly Jupiter Day, etc.

Tinnyday. Comes before or after Wednesday depending on daylight savings, encourages a beer or a wine (or whatever beverage of your choosing) to relax. Business hours the following day do not start until 10am.
Delivery fees from online retailers are ineligible to charge delivery fees, local food orders must include a free canned beverage, people working in entertainment venues get double time.