1. The document discusses Common Auxiliaries of Time (CAT) in the Universal Decimal Classification (UDC) system which represent the time of a subject rather than the publication date of a document.
2. CATs are placed in double quotations like "2022" to indicate the year, and can also represent decades, centuries, millennia, and ranges of times using various digit placements and symbols.
3. Special Auxiliary notations in the UDC are used to denote recurring concepts in different parts of the main classification table, though some notations may have different meanings depending on the main table.