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> commonly used in finance

Having worked in banking and hedge funds for many years for US, UK and European firms i have never once encountered this ISO calendar. I also part trained as an auditor when i started out, similarly never saw this. In fact this is the first time I've ever heard of it.

The day is pretty irrelevant in finance as it is too granular, but the problem of converting from US week numbers comes up.

Its also used in manufacturing, tire date codes for instance are week.year or year.week

Also used in supermarkets for planning. It's handy to see how much of product was purchased in week 34, spanning back a few years.

Used in all of retail. "Assortment Planning"

As far as I have seen finance prefers months and quarters, not being able to tell which year a month is in is a non-starter.

They do sometimes pretend each month is 30 days though.

This sounds nice — but is it really necessary to treat our good friend, the decimal point, so badly?

Calling today 44.7 means that we're effectively using base 7 after the decimal point (but it's 1 through 7 instead of the usual 0 through 6, for extra fun), while using base 10 before it.

Why not just something nice and easy-to-parse without all the mathematical confusion, like "44d7"?

> Why not just something nice and easy-to-parse without all the mathematical confusion, like "44d7"?

how about 5Nov44d7, much easier to parse. go with 5Nov43d6 and I'm on board even quicker because I prefer 0 indexing.

Which century is that?

If you prefer zeo indexing, you would want 4Nov43d6

i also have a competing preference to maintain communication with other people

As sibling mentioned, ISO already defines a standard notation (2023-W44-7), precisely so that different people don't have to go invent their own.

https://en.wikipedia.org/wiki/ISO_week_date

Fun fact: it's a dot, not a "decimal point".

That dot has many interpretations; in dates, sometimes it separates the month from year, or the day from a month. In version numbers, it separates major from minor, etc.

It's so much not a "decimal point", that in some languages (Hungarian and German, for instance) it is a thousands separator, whereas for decimal fractions a comma is used (10,000.00 in English is 10.000,00 in Hungarian, making Excel flip)

It is really just a dot. Our interpretation is what makes it a certain kind of separator. Or not a separator at all, like at the end of this sentence.

I don't agree. I'm from Belgium and I also use a comma, but that doesn't mean I would put hours and minutes as 8.35 or 8,35. No, it's 8:35.

Numbers with a dot or comma means it's decimal. Your date reference makes no sence because either / or - is used in those cases, not dots or comma's.

Basically, having a dot or comma adds to the confusion when working with non decimal numbers.

>Your date reference makes no sence because either / or - is used in those cases, not dots or comma's.

In my (european) country a dot is used - for example 5.11.2023.

Good point, the system would work just as well if it was something like:

w36:2

But it wouldn't cause nearly as much confusion or decimal place issues relating to improper automation.

> Numbers with a dot or comma means it's decimal.

But... It doesn't in IP addresses, version numbers, dates, with different locales, and possibly many other uses.

These examples clearly show that "numbers with a dot" doesn't always mean decimal.

A dot is a dot. Mainly with the _role_ of a separator. When you interpret it, it might mean a _decimal_ separator for you, but as well might mean a thousand-separator for MS excel with the German locale.

That depends on the country. For example, in Japan it is very common to write dates with either a dot, or with the full kanjis for year, month and day.

The ISO formatting for today is 2023-W44-7.

44d7 would be confusing for DnD users

It's just a ruse by Big Dice to get us to buy more d7s which traditionally has had very poor sales

> but is it really necessary to treat our good friend, the decimal point, so badly?

You’re not playing cricket, I guess. There, an over is six throws, and 4.3 overs is four and an half over.

> I think the best backwards-compatible calendar that we should adopt is the ISO week date calendar

The one where there are years without a new year’s day, and years with two?

https://en.wikipedia.org/wiki/ISO_8601#Week_dates

“As a consequence, if 1 January is on a Monday, Tuesday, Wednesday or Thursday, it is in week 01. If 1 January is on a Friday, Saturday or Sunday, it is in week 52 or 53 of the previous year (there is no week 00). 28 December is always in the last week of its year.”

Well that calendar has a new year's day, it's 01.1.

The problem is mapping it to your legacy calendar holiday, which like everything else is going to vary somewhat year by year.

no, the one where there are years without a january 1, and years with two january 1. there's nothing that says january 1 has to be new years, and in some cultures it already isn't. there's also nothing that says you can't continue celebrating january 1 as the new year, while using a week-day calendar for all official purposes.

a new calendar not mapping cleanly to the current months hardly seems like a valid criticism of a calendar that intentionally doesn't map to the current months.

I have no idea how this is better than just adding one month (say ("Festover") so we just continue as normal.

Aside from Halloween and NYE it will be very easy for people to get used to a 28 day month.

Because there's no confusion about whether you're talking about the new February or the old February. Is Feb 1 the 32nd day of the year or the 29th day?

i typically use day of year only, its super helpful, especially when calculating time between dates, or time until date. Also i use metric time which makes life even easier for to the second calcs. For many people, myself included, regular breaks through things like weekends do not truly exist so there is no point tracking them in the main date format. You might need it on occasion but it is information so rarely useful that recording it every time i write or use a date is wasted energy, especially when you consider how frequently you need to handle long range dates which DOY does more direct than day of week / week of year.

Just change to 73 5-day weeks and we’re golden.

Not sure if you’re serious, but the 7-day week as so entrenched that no system that breaks it will see any adoption. Maintaining the 7-day week and the 365 day year is non negotiable for any kind of calendar reform.

While we obviously can't change the length of the year in days, is there any actual reason to have a 7 day week beyond "that's what we've always done"?

That’s really a strong reason, is it not? I have no idea for how long humanity has tracked the seven day week, but suspect it’s been well over 2000 years.

That’s a lot of tradition to discard.

Goes all the way back to the Babylonians, 4000 years ago, at least

Alot of religions kinda use the week for weekly prayer (all Abrahamic religions) so you kinda stuck with it since you need to take that into account

Yeah, momentum. I can't think of what authority would be able to change it and make it be globally followed. A tradition of thousand years, with roots in religious texts. I don't think it is within anyone's power to change it.

7 days for the moon to go in half a cycle. Full to half. New moon to half moon. A pretty good demarkation of a period of time between one day and a month (full lunar cycle).

The moon cycle is approx 28 days, which is 7x4.

The height of tides are rooted in this but have 7 day periods of increasing, decreasing, increasing, decreasing.

I don't know if thats reason enough to continue with it, but possibly part of the history

This is a pretty common approximation, but the average lunation is closer to 29.5 days.

But those 365 days don't have to all fit into weeks. Take 364 days, divide those evenly into 7-day weeks, and then have the one (two if leap) new days be not part of the weeks. Call it Caturday or something. Hold a contest.

The fine article talks about that---there was Jewish resistance to the idea because they felt that the Sabbath was always the 7th day and that would get out of sync.

I always figured the funnest thing would just be not to give it a name, and then when people ask be like, well yesterday was Sunday and tomorrow is Monday.

But the more reasonable proposal I heard was just to call it New Years Day/Weekend, depending?

Day’ymcdayface. That’s how that will go down.

Referring to “boaty mcboatface”

Or 365.25 one-day months.

Just plain day number as the calendar is worse than weeks imo. We want to optimise for the common case, and wanting to know the day of week and number of weeks from today is much more common than day of year.

For example, “our next meeting is w48.3” is much more understandable than “day 339”.

It's indeed harder to compute the time difference, but maybe it's also an indication that mental calculation should be practiced more.

I don't see how. You are making assumptions and claims for others with no support. To me that week.day number looks more complicated and less meaningful than plain days.

Perhaps weeks seems to make sense since we sometimes use them for offsets and ranges, like "this project will take 6 weeks" and figuring out how many days that is is inconvenient. But if we were using days then we simply wouldn't use groups of 30 or 7 for things like that, we would use groups and multiples of 10 or 5. We'd probably end up using kilodays and millidays too instead of years or minutes, and years would be arbitrary, but 51.9something weeks is already arbitrary anyways.

And as that # of weeks example just showed, .day is ambiguous with decimal fractions of a unit.

All in all I see no special obvious rightness here. It's kinda crap actually.

Mr. I-Can't-Recognize-A-Joke here to explain in painful detail why your proposal won't work...

>Or 365.25 one-day months.

or 365.2425 one day months and no squabbles every 400 years. (we will however be squabbling the entire rest of the time)

If you put Christmas in month 0.24 I'm sold.

If making such a change, why not make it even simpler: use year + day number in year. e.g. today is 2023 day 309 (or day 308 if more sensible 0-based indexing would be used)

And keep the named 7-day week cycle as-is independently of that, this one has been going for millenia and we need some weekends after all

The 7-day cycle is so important to our lives that it's better to have a date notation for human consumption that includes it.

I know not to hope for it to ever catch on, but my dream date-time format would be:

year/day/hectosecond.second(.millisecond and so on to the desired precision)

The current date-time, to the second, would be 2023/308/342.65

The days, like the years and second-based units, are 0-indexed.

There are 100 seconds in a hectosecond, and normally 864 hectoseconds in a day.

And to go with it, I'd advocate either a "3-on, 2-off", or "6-on, 4-off" work cycle, depending on the nature of the work, or even just personal preference. This way, today(308) would obviously be on a "weekend" either way.

Ideally the beginning of the 2-day and 4-day weekends would be aligned, so both groups can party on a same evening

I imagine hectoseconds would be "fun" when dealing with timezones.

This is called the Julian (or Ordinal; I don't think there is a difference) calendar and is in wide use in (at least) parts of the US military for tracking things.

Actually, looking it up now it looks like the usage of the name "Julian" is due to the way the old tracking systems were programmed and used "JDATE" or similar. Nowadays it's just burned in habit that it's called the Julian Date.

There is Julian Day that is used in astronomy. It counts days since start of Julian period.

My guess is that the idea of counting days attached the "Julian" name to day number in a year.

Why even have years? Like Unix epoch, pick a start date, and just have the number of weeks increment indefinitely. If you really wish to do some separation, just say "last 50 weeks" or something.

This should be pretty obvious. We have years because seasons matter a lot, to a lot of people.

Like Julian days used in Astronomy?

https://en.wikipedia.org/wiki/Julian_day

so… are we going to talk about which day is day 1? because even here we can’t agree. this also translates to not having the same week number in certain years.

It is not commonly used in finance.