When the interface language is set to Korean, DataValue Time parser often does not recognize the ISO date properly.
Case 1: Recognizes the complete ISO date format (YYYY-mm-dd) as invalid date format
I was trying to edit [[d:Q7318]] to add start dates of head of state. I tried to add the start date "1934-08-02" and returned "invalid date format" message. "1934-08" returns Aug. 1934, but "1934-08-02" returned "invalid date format".
Case 2: Recognizes the 1st of month even the input is entered for other date.
When the date value is entered as "1773-12-16", the parser recognizes the date as "1776-12-01". When I entered the value "2014-10-04", the parser recognized "2014-10-01". You can find the case at https://www.wikidata.org/w/index.php?title=Q495366&action=history and https://www.wikidata.org/w/index.php?title=Q19024&action=history