Dates: DATE and TIMESTAMP.

DATE stores a calendar day (2024-02-15) with no time. TIMESTAMP stores a day and a time (2024-02-15 14:30:00). orders.order_date holds dates only. A date literal is written DATE '2024-02-15' or CAST('2024-02-15' AS DATE); both are clear to PostgreSQL. Dates compare with =, <, <=, >, >= like numbers: a later date is greater.

You can do arithmetic: order_date + 7 gives the date seven days later. When a DATE meets a TIMESTAMP in a comparison, the date is treated as midnight at the start of that day (2024-02-15 00:00:00), so '2024-02-15 10:00' is later than the date 2024-02-15.

These lessons use fixed dates only. Do not use CURRENT_DATE or now() — the result would change every day and grading could not be predictable.

Common mistakes: comparing with text that is not an ISO date ('15/02/2024'); mixing up > and >= right on the boundary; expecting a DATE to carry a time.

Small example:

SELECT id, order_date FROM orders WHERE order_date >= DATE '2024-03-01';