minimalDays

[sffc]

There were some potential concerns raised in the CLDR Design WG regarding minimalDays. Do we want to hold it back from Intl Locale Info?

@macchiati @markusicu @FrankYFTang

[FrankYFTang]

could you include the CLDR ticket here?

[sffc]

https://unicode-org.atlassian.net/browse/CLDR-17095

[FrankYFTang]

From https://unicode-org.atlassian.net/browse/CLDR-17095 this seems a non issue

[sffc]

Have been waiting for confirmation from the Google Calendar team for a while.

[FrankYFTang]

https://unicode.org/reports/tr35/tr35-dates.html#Week_Data

In order for a week to count as the first week of a new year for week-of-year calculations, the week beginning with firstDay must include at least the number of days in the new year specified by the minDays value; otherwise the week will count as the last week of the previous year (and for week-of-month calculations, minDays also specifies the minimum number of days in the new month for a week to count as part of that month).

Therefore, minDays is used to calcuate two information:

• the minimum number of days in the new year for a week to count as part of that year.
• the minimum number of days in the new month for a week to count as part of that month.

Now, why do we care which week is in which year or month?

Use case 1: AIDS Awareness Week

AIDS Awareness Week is last week in November, when extra effort is made to raise AIDS awareness.
https://en.wikipedia.org/wiki/AIDS_Awareness_Week

The "the last week in November" is therefore the week before "the first week in December" which depends on minDays.

Use case 2 National Map Reading Week

https://en.wikipedia.org/wiki/National_Map_Reading_Week
National Map Reading Week is an awareness campaign originally created by the Ordnance Survey, Britain's National Mapping Agency. It runs annually in the third week of October.

"the third week of October." is therefore two week after "the first week of October" which depends on minDays.

Use case 3: OCD Awareness Week

OCD Awareness Week ... takes place in the second week of October each year
https://en.wikipedia.org/wiki/OCD_Awareness_Week

"the second week of October" is therefore the week after "the first week of October" which depends on minDays.

Use case 4: World Immunization Week

World Immunization Week is a global public health campaign to raise awareness and increase rates of immunization against vaccine-preventable diseases around the world. It takes place each year during the last week of April

https://en.wikipedia.org/wiki/World_Immunization_Week
"The last week of April" is therefore the week before "the frist week of May" which depends on minDays.

[FrankYFTang]

the value is different per locale, not just calendar

(new Intl.Locale("en-US")).getWeekInfo().minimalDays
1
(new Intl.Locale("en-GB")).getWeekInfo().minimalDays
4
(new Intl.Locale("fr")).getWeekInfo().minimalDays
4
(new Intl.Locale("zh-CN")).getWeekInfo().minimalDays
1
(new Intl.Locale("de-DE")).getWeekInfo().minimalDays
4
(new Intl.Locale("es-MX")).getWeekInfo().minimalDays
1
(new Intl.Locale("es-ES")).getWeekInfo().minimalDays
4
(new Intl.Locale("en-CA")).getWeekInfo().minimalDays
1
(new Intl.Locale("ja-JP")).getWeekInfo().minimalDays
1

Therefore, "the Xth week of Month Y" could be a different week between US and UK.
because of this. In order for anyone to calculate which date is considered as the Xth week of Month Y for locale Z, the computation will need this value from locale Z.

[FrankYFTang]

So the first week of November 2024
in US is
October 27, Sunday - November 2, Saturday 2024
in France is
November 4, Monday - November 10, Monday 2024
and this calculation need both the firstDayOfWeek and also minDay to calculate

[sffc]

TG2 discussion: https://github.com/tc39/ecma402/blob/main/meetings/notes-2024-12-19.md#minimaldays-86

[sffc]

TG2 discussion: https://github.com/tc39/ecma402/blob/main/meetings/notes-2025-01-16.md#minimaldays

[sffc]

I posted some feedback on the CLDR issue: https://unicode-org.atlassian.net/issues/CLDR-17095

Key points from feedback I received from internal clients:

• Users in Europe who changed their locale to en-US got unexpected week numbers since en-US applies different rules, and they filed bug reports.
• Upon changing all locales (including en-US) to ISO week numbers, there was a small amount of criticism, but overall the number of bug reports went down.

This implies that people who care about week numbers tend to use ISO week numbers, though not universally, and that the locale may not be the best way to determine week numbering.

[FrankYFTang]

Per discussion in TG2- remove the minimal days- PR in #99

[sffc]

TG2 discussion on 2025-02-06: https://github.com/tc39/ecma402/blob/main/meetings/notes-2025-02-06.md#localeinfo-minimaldays