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Does anyone know the history of the common date format that the ISO week date is based on. The Wikipedia article mentioned it was previously known as "Industrial date coding". Usually, it looks something like 2019w10 or 2019-w10 or 19w10, for the 10th week of the year 2019. See ISO 8601 for the current ISO definition.

It seems like a format from another era where delivering something the "week of" was close enough. Something like "Ya I can get those 20 tons of coal to you by 1890w04". Did this come out of business delivery dates or some sort of government standard? Is it still relevant today, where waiting two hours for an Amazon package taxes our patience?

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    Clearly you don’t deal with large procurements with long lead times in a manufacturing environment. Sometimes delivery in quarter 3 in 2021 is good enough for planning purposes. – Jon Custer Mar 7 at 23:49
  • I do not but I thought the trend was "just in time delivery" where the new sheet metal gets stocked just as the last piece of the old stock is welded to the car. – Dweeberly Mar 8 at 0:06
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    More likely to come from manufacturing organizations that have a payday every Friday. For most businesses the most important planning expenditure has always been payroll. – Pieter Geerkens Mar 8 at 2:06
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(I'm not sure I've got an answer, but I've got some research that may help someone else find a better answer).

The practice appears to be commonplace in European commercial and industrial applications.

In commercial and industrial applications (delivery times, production plans, etc.), especially in Europe, it is often required to refer to a week of a year. Week 01 of a year is per definition the first week that has the Thursday in this year, which is equivalent to the week that contains the fourth day of January. In other words, the first week of a new year is the week that has the majority of its days in the new year. Week 01 might also contain days from the previous year and the week before week 01 of a year is the last week (52 or 53) of the previous year even if it contains days from the new year. A week starts with Monday (day 1) and ends with Sunday (day 7). For example, the first week of the year 1997 lasts from 1996-12-30 to 1997-01-05 and can be written in standard notation as 1997-W01 or 1997W01 Kuhn

. . . for applications like industrial planning where many things like shift rotations are organized per week and knowing the week number and the day of the week is more handy than knowing the day of the month. Ibid

Mr. Geerkens points out

"More likely to come from manufacturing organizations that have a payday every Friday. For most businesses the most important planning expenditure has always been payroll."

This week numbering scheme was introduced earlier by the ISO with the standard ISO 2015:1976 (Numbering of Weeks) and was repealed on 1 June 1988 with the imminent introduction of ISO 8601. The calendar defined in the ISO standards 2015 and 8601 is commonly referred to as the “ISO calendar”. Gent

Implies that while this may have been common practice, it was introduced by ISO. I think it more likely that Mr. Geerkens is correct and this merely codified an existing practice.

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