OSM translation
In my opinion, the OSM developers should not even use such abbreviated notation, which is clearly ambiguous or at least not abvious (compare "2000-09" and "2000-19", the first at least is a standard notation for month numbers in year , but what is month 19 in year 2000?). Looks like they were lazy when typing it, assuming that it was clear for them, but everyone wonders how to interpret it, or could incorrectly infer this means "2000-1-9" i.e. with a typo, or that there was a missing month, or that this meant the 19th day of the year, so on 19 January 2000).
A copyright statement is very formal and must be extremely clear. Such notation is never used in CLDR localisations in English and not found in any formal/legal documents. Anyway, all translations should absolutely not reuse this non -standard abbrevation and translate (transliterate, transnumerate) as if it was "2010–2019". This is what almost all translations have done already (correctly, e.g. Osm:Site.copyright.legal babble.contributors gb html/fr). But the official OSM website is still lagging there since long in its very important copyright page that every other site must link to.
Why don't they fix this non-sense that does not even have any meaning in UK whose laws strongly apply to this copyright notice ? Couldn't it be changed directly here in this wiki (or at least documented in the "/qqq" as long it is not fixed by OSM developers submitting their source pack to be translated here). Not fixing it even in English could have legal consequences, notably if someone claims in a court (and that's defendable) that OSM made a legally invalid copyright statement, and then wants to use and republish/resell OSM data with their own proprietary copyright by discarding/ignoring as well the licence conditions.
If some technical admin at OSM does not care about it, at least we should contact the OSM Foundation to force them to fix it (this is in the interest of the whole OSM community and all valid reusers of OSM data, including in commercial applications, or in organizations which could be threated by legal suites to pay a third party that was the first one to make a valid copyright statement, i.e. with a valid date).