DateServices.isWorkingDay

Returns true if the date is configured as a non-working day in the organisational calendar, otherwise false. The organisational calendar can be configured using the Server Administration application.

Javascript example:

 // check is today a working day
 if (DateServices.isWorkingDay(new Date())
 ..
 // check specific date is a working day
 if (DateServices.isWorkingDay(new Date(fields.DATE_FIELD.value))
 ..