The standard date/time field extract function is supported for Day, generating EXTRACT(DAY FROM date/time expression). If this function is applied to a column or expression of type other than Date or Timestamp, a SQL runtime error will occur. When dragging an Extract Day function into a variable, the following tree element is created.
Columns and/or other expressions/literals that resolve to a date or timestamp can be moved over the (empty) branch of the tree.
The type of the value returned is integer. There are no special properties for the Extract Day function.