:M{1,2} - ''month, zeroed filled to number of specified digits''
:D{1,2} - ''day, zeroed filled to number of specified digits''
:d or ddd - 1 ''1 to 3 digit day of the year (1-365) (should be only 1 or 3 digits; 3 digits zero fills)''
:N+ - ''auto incrementing number, zeroed filled to number of specified digits (i.e. N or NNN or NNNNN => 1 or 001 or 0001)''
:a+ - ''auto incrementing lowercase string, a filled to number of specified digits''