The Observance of a recurring holiday can be specified from within the type tab of the recurrence options.
This setting allows you to specify that a holidays is not a general holiday that applies to everyone in the entire country. The various types of observance are grouped in 3 main categories: Geographical (municipal, regional, ...), Sectorial (public sector, banks, private sector), and religious.
The observance of a holiday is not used in basic holiday tokens, but its value can be obtained from the function GetHolObservanceFromTable in macros to ignore or shade or otherwise treat specially partial holidays (ie. holidays whose observance is not blank).