No; users of the style cannot override this. It may only be defined in the style.
|dayshort||Day of week. Short form. Example: Mon, Tue, Wed...|
|daylong||Day of week. Long form. Example: Monday, Tuesday, Wednesday...|
|monshort||Month. Short form. Example: Jan, Feb, Mar...|
|monlong||Month. Long form. Example: January, February, March...|
|yy||Year, two digit.|
|yyyy||Year, four digit.|
|dth||Day plus ordinal. 1st, 2nd, 3rd, 4th, 5th...|