I run into this datetime problem in et.wiki, with displaying wikidata population date in city infobox.
For example in article https://et.wikipedia.org/wiki/Vilnius the wikidata population date "2014" becomes "30.11.2013". And when I modify the wikidata module to take the precision into account then "2013" is displayed as date.
It could be something I'm overlooking in wikidata module https://et.wikipedia.org/wiki/Moodul:WikidataDev or in city infobox template https://et.wikipedia.org/wiki/Mall:Linn.
No problems with population dates were the precision is one day.
-- Raul