What is the difference between DATETIME and TIMESTAMP in MySQL?

Both store date and time values, but with important differences: DATETIME: stores date and time literally as entered: "YYYY-MM-DD HH:MM:SS"; range: 1000-01-01 to 9999-12-31; 8 bytes; NOT affected by timezone — stores what you give it, returns what it stored. If you insert "2024-01-15 10:00:00" in New York timezone, it stores and returns exactly that, regardless of the server's timezone. TIMESTAMP: stores as UTC internally (Unix timestamp) and converts to/from the current session timezone on read/write; range: 1970-01-01 00:00:01 UTC to 2038-01-19 03:14:07 UTC (the 2038 problem!); 4 bytes (more space-efficient); supports automatic initialization and update: created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP, updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP. Use TIMESTAMP when: you need timezone-aware storage (display different times to users in different zones); recording when something happened. Use DATETIME when: you store user-facing calendar dates/times that should not change with timezone (appointment slots, event dates); you need dates outside TIMESTAMP's 1970-2038 range. Always store times in UTC in your application layer for maximum clarity.