Long time formats for Czech do not include number of hours

Hello,

it seems that the definition of long time formats for the Czech language (in https://github.com/date-fns/date-fns/blob/master/src/locale/cs/_lib/formatLong/index.ts#L11) uses H instead of HH unlike other locales. This then results in weird behavior when switching between languages because strings like 1 hours 15 minutes change to hour 15 minutes (in Czech).

This behaviour was encountered in jellyfin-vue that uses date-fns 2.28.0 (https://github.com/jellyfin/jellyfin-vue/blob/master/package.json#L46).

[KucharczykL]

Hope I won’t sound too aggressive but it should have been asked what are the reasons and use cases for omitting the number, not the other way around (asking why the number should be included). Having a number is the default and never wrong. Not having a number is change from the default and can sometimes be wrong or odd.

[fturmel]

Interesting. So, maybe this is just the wrong way to build a localized media duration string? How should a project like Jellyfin approach this problem? Is this a blind spot of date-fns that should be considered?

@KucharczykL @janziemba could you share some use cases that would require to have or not have the number 1, just so we can document them?

For the sake of comparison, here are all locales using formatDuration and Intl.NumberFormat (❌ indicates no support in Chrome 97, will fallback to system’s default locale)

results table

locale	date-fns formatDuration	Intl.NumberFormat	same?
af	1 uur 15 minute	❌
ar	ساعة واحدة 15 دقيقة	ساعة 15 دقيقة
ar-DZ	ساعة واحدة 15 دقيقة	ساعة 15 دقيقة
ar-EG	ساعة 15 دقيقة	ساعة ١٥ دقيقة
ar-MA	ساعة واحدة 15 دقيقة	ساعة 15 دقيقة
ar-SA	ساعة واحدة 15 دقيقة	ساعة ١٥ دقيقة
ar-TN	ساعة 15 دقيقة	ساعة 15 دقيقة	✅
az	1 saat 15 dəqiqə	1 hour 15 minutes
be	1 гадзіна 15 хвілін	❌
bg	1 час 15 минути	1 час 15 минути	✅
bn	১ ঘন্টা ১৫ মিনিট	১ ঘন্টা ১৫ মিনিট	✅
bs	1 sat 15 minuta	1 hour 15 minutes
ca	1 hora 15 minuts	1 hora 15 minuts	✅
cs	hodina 15 minut	1 hodina 15 minut
cy	1 awr 15 munud	❌
da	1 time 15 minutter	1 time 15 minutter	✅
de	1 Stunde 15 Minuten	1 Stunde 15 Minuten	✅
de-AT	1 Stunde 15 Minuten	1 Stunde 15 Minuten	✅
el	1 ώρα 15 λεπτά	1 ώρα 15 λεπτά	✅
en-AU	1 hour 15 minutes	1 hour 15 minutes	✅
en-CA	an hour 15 minutes	1 hour 15 minutes
en-GB	1 hour 15 minutes	1 hour 15 minutes	✅
en-IE	1 hour 15 minutes	1 hour 15 minutes	✅
en-IN	1 hour 15 minutes	1 hour 15 minutes	✅
en-NZ	1 hour 15 minutes	1 hour 15 minutes	✅
en-US	1 hour 15 minutes	1 hour 15 minutes	✅
en-ZA	1 hour 15 minutes	1 hour 15 minutes	✅
eo	1 horo 15 minutoj	❌
es	1 hora 15 minutos	1 hora 15 minutos	✅
et	üks tund 15 minutit	1 tund 15 minutit
eu	1 ordu 15 minutu	❌
fa-IR	1 ساعت 15 دقیقه	۱ ساعت ۱۵ دقیقه
fi	tunti 15 minuuttia	1 tunti 15 minuuttia
fr	1 heure 15 minutes	1 heure 15 minutes	✅
fr-CA	1 heure 15 minutes	1 heure 15 minutes	✅
fr-CH	1 heure 15 minutes	1 heure 15 minutes	✅
fy	1 oere 15 minuten	❌
gd	1 uair de thìde 15 mionaidean	❌
gl	1 hora 15 minutos	❌
gu	1 કલાક 15 મિનિટ	1 કલાક 15 મિનિટ	✅
he	שעה 15 דקות	שעה 15 דקות	✅
hi	१ घंटा १५ मिनट	1 घंटा 15 मिनट
hr	1 sat 15 minuta	1 sat 15 minuta	✅
ht	1 lè 15 minit	❌
hu	1 óra 15 perc	1 óra 15 perc	✅
hy	1 ժամ 15 րոպե	❌
id	1 jam 15 menit	1 jam 15 menit	✅
is	1 klukkustund 15 mínútur	❌
it	un’ora 15 minuti	1 ora 15 minuti
ja	1時間 15分	1 時間 15 分
ja-Hira	1じかん 15ふん	1 時間 15 分
ka	1 საათი 15 წუთი	❌
kk	1 сағат 15 минут	❌
km	1 ម៉ោង 15 នាទី	❌
kn	1 ಗಂಟೆ 15 ನಿಮಿಷಗಳು	1 ಗಂಟೆ 15 ನಿಮಿಷಗಳು	✅
ko	1시간 15분	1시간 15분	✅
lb	eng Stonn 15 Minutten	❌
lt	valanda 15 minučių	1 valanda 15 minučių
lv	1 stunda 15 minūtes	1 stunda 15 minūšu
mk	1 час 15 минути	❌
mn	1 цаг 15 минут	❌
ms	1 jam 15 minit	1 jam 15 minit	✅
mt	siegħa 15 minuti	❌
nb	en time 15 minutter	1 time 15 minutter
nl	1 uur 15 minuten	1 uur 15 minuten	✅
nl-BE	1 uur 15 minuten	1 uur 15 minuten	✅
nn	ein time 15 minutt	❌
pl	godzina 15 minut	1 godzina 15 minut
pt	1 hora 15 minutos	1 hora 15 minutos	✅
pt-BR	1 hora 15 minutos	1 hora 15 minutos	✅
ro	1 oră 15 minute	1 oră 15 minute	✅
ru	1 час 15 минут	1 час 15 минут	✅
sk	hodina 15 minút	1 hodina 15 minút
sl	1 ura 15 minut	1 ura 15 minut	✅
sq	1 orë 15 minuta	❌
sr	1 сат 15 минута	1 сат 15 минута	✅
sr-Latn	1 sat 15 minuta	1 sat 15 minuta	✅
sv	en timme 15 minuter	1 timme 15 minuter
ta	1 மணி நேரம் 15 நிமிடங்கள்	1 மணிநேரம் 15 நிமிடங்கள்
te	ఒక గంట 15 నిమిషాలు	1 గంట 15 నిమిషాలు
th	1 ชั่วโมง 15 นาที	1 ชั่วโมง 15 นาที	✅
tr	1 saat 15 dakika	1 saat 15 dakika	✅
ug	بىر سائەت مىنۇت 15	❌
uk	1 годину 15 хвилин	1 година 15 хвилин
uz	1 soat 15 minut	1 hour 15 minutes
uz-Cyrl	1 соат 15 дақиқа	1 hour 15 minutes
vi	1 giờ 15 phút	1 giờ 15 phút	✅
zh-CN	1 小时 15 分钟	1小时 15分钟
zh-HK	1 小時 15 分鐘	1 小時 15 分鐘	✅
zh-TW	1 小時 15 分鐘	1 小時 15 分鐘	✅

source code

import { formatDuration } from "date-fns";
import * as locales from "date-fns/locale";

function dateFnsFormat(locale) {
  return formatDuration(
    { hours: 1, minutes: 15 },
    {
      format: ["hours", "minutes"],
      locale
    }
  );
}

function intlFormat(localeCode) {
  if (Intl.NumberFormat.supportedLocalesOf(localeCode).length === 0) {
    return "❌";
  }

  const hours = new Intl.NumberFormat(localeCode, {
    style: "unit",
    unit: "hour",
    unitDisplay: "long"
  }).format(1);

  const minutes = new Intl.NumberFormat(localeCode, {
    style: "unit",
    unit: "minute",
    unitDisplay: "long"
  }).format(15);

  return hours + " " + minutes;
}

console.log("|locale|date-fns formatDuration |Intl.NumberFormat|same?|");
console.log("|-|-|-|-|");

Object.values(locales)
  .sort((a, b) => a.code.localeCompare(b.code))
  .forEach((locale) => {
    const a = dateFnsFormat(locale);
    const b = intlFormat(locale.code)
      // some `fr` locales use non-breaking spaces
      .replace(String.fromCharCode(160), " ");
    const areSame = a === b ? "✅" : " ";

    console.log("|", locale.code, "|", a, "|", b, "|", areSame, "|");
  });