The manner in which the three numbers, when written, are set off from each other. Whether the numbers less than 10 are written with a leading zero. Whether there are limits to the dates which can be expressed. The year is expressed in the manner of the astronomers and chronologists. With the use of this astronomical system of year-numbering there are no limits to the dates which can be expressed in this date format.
Some lunar calendars add an extra month to some years.
If this follows the last month of a normal year then the number of the month is simply one more than the number of months in a normal year. It is, however, accommodating. Consider, e.g., a calendar involving months which counted the days from 1 to 15 but then counted down to 1.