PostgreSQL 18 introduces temporal constraints, enhancing the management of time-based data by integrating temporal data integrity directly into schema definitions through features like WITHOUT OVERLAPS for primary keys and PERIOD for foreign keys. This innovation simplifies maintaining referential integrity across temporal relationships, allowing databases to manage complex time-based constraints without extensive application-level code. An example using a fictional restaurant booking system, King Crab, demonstrates how these constraints prevent overlapping periods for table reservations, ensuring that bookings are only made within available time slots. Although there are limitations, such as the lack of support for certain actions in ON DELETE and ON UPDATE clauses for temporal foreign keys, the new features facilitate efficient querying of temporal data, making it easier to build robust applications by leveraging specialized operators and functions to handle time ranges. PostgreSQL 18's temporal constraints represent a significant advancement in database management, allowing developers to maintain complete historical data and complex relationships within the database itself.