%?[date] special texts
Apart from different representations of a weekday name, it is possible to create its weekday number. Likewise, the current day-of-year number, the day number, the week number, the month name, the month number, the year number, the Moon phase, the biorhythm, and some useful difference values can be produced.
For the date argument these
special text may have, the following rules concerning definite omission
values are valid, elucidated by using the
0000, the current year is assumed for the year.
00, the current month is assumed for the month, and the December is assumed in case mm is set to
00, the current day is assumed for the day, and the last day of the month is assumed in case dd is set to
9), then a www field must also be specified.
 The succeeding rules are analogously valid for the other permitted date formats.