A local Date object where 0 <= year <= 9999 can be
formatted to a common ISO 8601 format YYYY-MM-DD with:-
/** Formats a Date to YYYY-MM-DD (local time), compatible with both
* ISO 8601 and ISO/IEC 9075-2:2003 (E) (SQL 'date' type).
* @param {Date} dateInRange year 0000 to 9999.
* @throws {RangeError} if the year is not in range
*/
function formatDate(dateInRange) {
var year = dateInRange.getFullYear(),
isInRange = year >= 0 && year <= 9999, yyyy, mm, dd;
if(!isInRange) {
throw RangeError("formatDate: year must be 0000-9999");
}
yyyy = ("000" + year).slice(-4);
mm = ("0" + (dateInRange.getMonth() + 1)).slice(-2);
dd = ("0" + (dateInRange.getDate())).slice(-2);
return yyyy + "-" + mm + "-" + dd;
}