One of the date examples shows a box with "06/09/2016" in it, with an error popup which says "Please select a valid value. The two nearest valid values are 2016

One of the date examples shows a box with "06/09/2016" in it, with an error popup which says "Please select a valid value. The two nearest valid values are 2016-06-06 and 2016-06-11". Seems incoherent to use US date format for the box and ISO8601 format for the error message. Also I wish software in general would stop trying to guess what the locale settings should be and just ask. I have my language set as en_US but I prefer to use 24h time and ISO8601 dates. With this update Firefox guesses wrongly 12h time and mm/dd/yyyy date format with no way to override it that I could find.