Thanks for the nice overview, i'm a bit confused about the commercial statements. I tried to make a table to visualize the shifts:
{LINK REMOVED}https://i.snag.gy/qg9pMR.jpg

So do i understand correctly that:
Low density Commercial only has an extended workshift, and also works in the weekend.
High density Commercial has three shifts does not work in weekends
Commercial Tourism has 3 shifts, also in weekends?
Commercial Leiser only works in weekends, only 1 shift?

I wash thinking perhaps we could feed such a table to the mod by an XML file or something so users have full control?

Next to that im a bit worried about the garbage processing, that is not ongoing on weekends?

One last question:
Do the workshifts have impact on the production of a building? IE, the industry does not produce in the weekends, and therefore hardly any trucks/cargotrains are driving around the map? (would be cool)

Commercial Leisure works 24/7 because all commercial buildings have 3 work shifts. So the table you linked is not quite correct.
Despite having no workers, the garbage trucks will be doing their job even on Weekends. For the same reason, the cargo trucks and trains will operate on Weekends too. The work shifts only impact the citizens movement but not the economy/cargo logistics. This is something for an economy mod, I think. I will not implement this in Real Time.

Thanks for the clarifications. I've tried to update the table:
{LINK REMOVED}https://i.snag.gy/0g9i5L.jpg
I've assumed that all Commercial is doing 3 shifts on workdays and on weekends.

That is incorrect. Commercial High doesn't work on Weekends, as well as Commercial Eco (if you have the Green Cities DLC) while Beautification and Parks do.

I've got a query relating to Commercial High in that case. Is there something built-in to the mod that prevents these buildings becoming abandoned due to no customers on weekends?

The fact that citizens don't go to work on Weekends doesn't affect anything. The game only checks whether there are enough assigned workers. So the work shifts have no impact. If your buildings get abandoned, then there are either not enough workers in your city, or not enough customers, or maybe some other problems. The mod has nothing special to prevent that, it only causes the problem timer to run slowly (so you have more time to fix the issue).

If you want to aim for extra realism, consider making ore specialization take less time off. Mines are basically 24/7/365 operations irl.

cite: best friend is a mining engineer. Those guys don't quit!

Originally posted by Owlchemist:

If you want to aim for extra realism, consider making ore specialization take less time off. Mines are basically 24/7/365 operations irl.

Tracked it down on GitHub as a feature. Will appear in an upcoming release.

I wonder about things like agriculture, logging, and the organic commercial businesses? Most farmers work all week.

Originally posted by Althazar:

I wonder about things like agriculture, logging, and the organic commercial businesses? Most farmers work all week.

This is now implemented.

Tried to make a new overview:
https://imgur.com/a/OVS3hIe

I wonder why Commercial Low is working on weekends (especially Sunday, Saturday is fine), and also why does Commercial have 3 shifts? I may not understand the relationships between the different things in game correctly, but when Commercial really just refers to where people go to buy stuff, then anything other than one shift, and no work on sundays seems not so realistic to me? Work on Sundays may depend on the country you live in, but i haven't seen a single i.e. grocery store, that was operating on sunday night at 03:30 in the morning.... Seems very unrealistic to me..

2-2 shifts? 8:00 to 20:00 day+night?
Non-stop industry and services uses that on constant basis.

Suggesting that students show up to school for the scheduled time instead of the earlier time cause it is kind of unrealistic that students show up at school at 3/4 for school which starts at 8/9 o'clock.

Another suggestion is that instead like @th0bse the low commercial be closed on weekends while high density is open on weekends seeing as how high has the manpower .

Is there any way to modify those hours by users? Also, are there any specific reasons why commercial high are open during the night but not on weekends? This is very unrealistic.