Communicating that plural is now supported

This doesn't seem to support language specific plural rules? My concern is that translators will expect it to work like MediaWiki plural rules, given the syntax looks same, but currently it works differently.

See also https://translatewiki.net/wiki/Plural

Why are English resources using capitalization everywhere? This suggests incorrect capitalization when formatted dates are inserted in sentences, whereas capitalization will be contextual (and can be forced noly when we know this is the start of sentence, e.g. by using {{Ucfirst:}} in Mediawiki). This also applies to weekday names, month names and season names (also not capitalized in most languages, even if English capitalizes weekday names and month names).

Note that I used PLURAL in French for formating "1er janvier 2000" instead of "1 janvier 2000" (the ordinal suffix "er" only applies to the 1st day of the month, there's no suffix for all other days of the month; the PLURAL rule is usable here, even if 0 is also singular but not used for days of the month; all other niteger values are plural in French, so there's no ordinal suffix).

Also another note: it is not clear that for intervals (using "from" and/or "to") the date/time in parameter includes a date (with optional time), or just a time or an imprecise date. This affects how we translate the preposition:

• "du 1er janvier 2000 au 31 décembre 2000" (note the change from "de" to "du", and "à" to "au")
• "du 1er janvier au 31 décembre"
• "de janvier à décembre" (interval of months ; but note also the additional case "d'avril à octobre", where we need a contraction of "de" with an apostrophe and no space)
• "de janvier 2000 à décembre 2001" (same remark)
• "de 2000 à 2001" (interval of years)
• "de 12h30 à 20h30" (interval of times)
• "du 1er janvier 2000 à 08h30 jusqu’au 31 décembre 2000 à 18h" (note the change from "de" to "du", and "à" to "jusqu’au" because "à" is used for the time on both ends)

This also affects non-intervals for the choice of prepositions meaning "at/on/in" (if there's one) as this preposition changes depending on the date/time precision:

• "le 1er janvier"
• "en janvier"
• "en janvier 2000"
• "en 2000"
• "à 12h30"

All these cases are already handled using CLDR data for date formatting (and it supports many more calendars, and all kinds of intervals and precisions).