A function.
| arg | An instance of <date>. |
| val | An instance of <integer>. |
| val | An instance of <integer>. |
| val | An instance of <integer>. |
| val | An instance of <integer>. |
| val | An instance of <integer>. |
| val | An instance of <integer>. |
| val | An instance of type-union(singleton(#”monday”), singleton(#”wednesday”), singleton(#”friday”), singleton(#”saturday”), singleton(#”sunday”), singleton(#”thursday”), singleton(#”tuesday”)). |
| val | An instance of <integer>. |