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I try to promote the usage of ISO8601. How can every month of any year and halves of theses months be represented in ISO 8601? We use a perpetual calendar in Excel where there are 2 column headers : first row is January, February, etc. and below a column subdivided into 2, something like this following example:

       | Tasks  | January | February |  March   | ...
       |        |    |    |     |    |     |    | ...
       |  task1 |    | X  |     |  X |     |    | ...
       |  task2 |    |    |  X  |    |     |    | ...

How to best merge these header rows into in a meaningful row, written Jan-<first half> | Jan-<second-half> | etc. in an easily readable form. I think January-01 | January-02 is obviously not the answer. If this is not the right way to do it, please, describe how to deal with this kind of repetition.

This question is different from the one about representing date ranges I've redirected to as in the later start and end years/dates are indicated. My question is about recurring approximate date spans.

halfer
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jgran
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  • Does this answer your question? [Is there any kind of standard for representing date ranges?](https://stackoverflow.com/questions/20413843/is-there-any-kind-of-standard-for-representing-date-ranges) – Mark Baijens Apr 15 '22 at 10:35
  • Thanks. Not exactly, as I don't need the year, just _every January_, or more precisely _every first half of January_, and a notation like `R/--01/P2W` is too complexe compared to plain english. My requirement might be out of scope of the ISO 8601 standard. – jgran Apr 15 '22 at 10:41
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    May I ask why you want to do it in regulation with the ISO 8601 standard. The standard is mainly used for uniform way of storing and communicating a date. The visual representation of that date is often done by conversion to a date format according to a locale standard or predefined format. – Mark Baijens Apr 15 '22 at 12:20
  • Well, because I promote ISO8601 as many others do on the web, and I don't know the scope (the full standard is not available as any ISO standard). So I try to translate what people write into the standard, if feasable, like recurring date `R/P1Y` for saying every year. `Every January`, without any year, might not writable, I just don't know... – jgran Apr 15 '22 at 12:39
  • The ISO 8601 standard is great, but useless when used in a wrong way. It's not a method to present a readable date or date range. It's a method the make sure we talk about the same date when communicating about it. Therefore you often see it in automated interface messages (XML, JSON). If you want to present a date range visually to a user then I would just use "First half of Januari" or "01-01-2022 till 15-01-2022" (accordings to the users locale date format and language). – Mark Baijens Apr 15 '22 at 13:05
  • Thanks again. So there is not equivalent unambiguous representation of 'Fist half of January _every year_' (not of a specific year ? (I wouldn't use 01-01-2022 in any case but **2022-01-01/01-15** ;-) as recalled in this question [https://stackoverflow.com/questions/20413843/is-there-any-kind-of-standard-for-representing-date-ranges](https://stackoverflow.com/questions/20413843/is-there-any-kind-of-standard-for-representing-date-ranges). – jgran Apr 15 '22 at 13:24
  • Not that i'm aware of. You basicly don't have a date anymore but 24 blocks. You could just store that as an integer (0-23) and write a conversion function to present it to your users in a friendly way. – Mark Baijens Apr 15 '22 at 13:39
  • A problem I am having with it is that I don’t consider “first half of January” that well-defined. For this reason I’d be surprised if ISO 8601 nevertheless includes a representation for it. Would that in January be until 12 noon on the 16th and in February in a non-leap year until 12 midnight on the 15th? And if summer time begins in March, should I then subtract half an hour? – Ole V.V. Apr 17 '22 at 18:14
  • I admit these dates are fuzzy, but convenient for recurring tasks and should be seen as rough dates in projects, _around this period_. I'm giving this example `every January` or `every half of January`, but it could also be `months divided in 4 weeks` or `every first quarter`, without specifying year. It's understandable that it's not included in the scope of ISO 8601:2019. My confusion stems from the notion of **recurring time interval**, specifically in [§ 4.5.4 Representations other than complete](https://www.loc.gov/standards/datetime/iso-tc154-wg5_n0038_iso_wd_8601-1_2016-02-16.pdf). – jgran Apr 19 '22 at 07:38

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