600 Subfield $y - Chronological subdivision:

Subfield $y contains a subject subdivision that represents a period of time. Subfield $y is appropriate only when a chronological subject subdivision is added to a name or name/title.

Examples:

600 10$aShakespeare, William,$d1564-1616$xCriticism and interpretation$xHistory$y18th century.

600 10$aReagan, Ronald$xAssassination attempt, 1981.

[Date is part of the general subdivision.]