How to create a time attribute relationship (1)

Thanks to Google Analytics I saw that many page hits on my blog result from keyword searches for "create time attribute relationship". And in fact, it seems to be more complicated to do a proper attribute relationship modeling with the time dimension than with most other dimensions. The reason for that is simple: The time dimension involves many related attributes (e.g. months can be written as number, short- and longname) and parallel hierarchies (like calender and fiscal view or calender weeks).