Any item of information that can be derived from a date could be stored in the calendar table if it simplifies or improves the performance of queries or code.

Whether or not the data items you mention should be added to the calendar table is an implementation decision, but they all seem plausible candidates.

It is quite normal for a calendar table to have more than 20 data items, e.g. http://arcanecode.com/2009/11/18/populating-a-kimball-date-dimension/