Have they come up with any estimate of the global cost of the switch, and compared that to the benefit of the new calendar? It seems to change a bunch of stuff, and add a complicated new "leap week", for no particularly good reason. Yeah, it might reduce the cost of printing calendars slightly, though a lot of people use new calendars yearly so they can write on them, and a lot more just use their computer.

The cost of the transition would not be insignificant. In the Western world, we've had two major calendar changes in the past 2200 years or so. The most recent one, the transition from the Julian calendar to the Gregorian calendar, lasted for about 400 years, as different countries transitioned at different times, with, I'm sure, plenty of friction caused by the lack of synchronization. Is it really necessary to go through all of that again?

Also, while this proposal would make holidays based on the solar calendar fall on the same day every year, it would do nothing for the holidays based on the lunar calendar. They would still drift around.

Reading their proposal on cato.org linked to from the article, it seems that a large part of their motivation is the synchronization of calendars for various financial instruments. But that doesn't require changing everyone's calendar; you can fix just the financial instruments, which already don't follow the ordinary calendar, without wreaking havoc on every other use of the calendar.

And I'm not sure how this extra week in December ever few years is supposed to help solve the problems with financial instruments. Under the current system, you need to deal with the fact that months may differ in length by up to 3 days, and that needs to be dealt with every month; in the new system, months would regularly vary by 1 day, but suddenly vary by another 7 days once every 5 years or so.

I think one of the reasons we've gotten ourselves into this mess is that we keep on trying to fit together different cycles of arbitrary length such that they match up exactly, which is impossible, so we add hacks on top of hacks to try to fix the problem. We try to make the cycle of days match the cycles of years, we try to make the cycle of months match the cycle of days (and years), and this proposal tries to shoehorn the cycle of weeks into that too, with a hack that adds an extra week every 5 or 6 years seemingly at random (while there is a regular rule for it, it's not as easily remembered as the Gregorian "leap year every 4 years, except for years divisible by 100, but an exception to that exception for years divisible by 400").

Instead of trying to do hacks to get all of these cycles to line up, why not move in the other direction and take the approach of having regular cycles at different frequencies that do not line up? You can have a financial calendar of 30 solar days (or whatever period is most convenient for you), a lunar calendar of one lunar month, the 7 solar day week, the tropical year that aligns with the seasons, the sidereal year that aligns with the orbit of the earth around the sun (which differs from the tropical year due to precession of the earth's axis). We have computers that can keep track of how all of these things line up when we care these days; instead of trying to simplify everything to fit together discretely with hacks added to fix it up, just let the computers deal with the precise details and allow each cycle to be simple and independent.

Now, moving to a single worldwide time standard (just use UTC for everyone for everyday use) seems to make a little more sense. While I understand the desire to make the hours line up with the solar day in a reasonably uniform way around the world, timezones (and daylight savings time) are an ugly hack that add a lot of cost and give you only a very rough approximation of what you are trying to achieve.