Choosing the Right MySQL Date/Time Type: DATETIME vs TIMESTAMP vs Unix Timestamp

When developing software, storing time information correctly is essential for business logic, logging, and data integrity. This article helps developers reassess MySQL's date/time storage options and choose the most suitable type for their scenarios.

Don’t store dates as strings

Beginners often use VARCHAR to store dates like "YYYY‑MM‑DD HH:MM:SS" because it looks simple, but this approach has two major drawbacks:

Space inefficiency : strings consume more storage than native date/time types.

Query and calculation inefficiency :

Complex and slow comparisons : string comparison follows lexical order, e.g., "2024-05-01" < "2024-1-10", and is slower than numeric date comparisons.

Limited calculation functions : you cannot directly use MySQL's rich date functions without conversion.

Poor index performance : range queries on string indexes are less efficient than native date indexes.

DATETIME vs TIMESTAMP selection

DATETIME

stores the literal date and time value without any timezone information. The value you insert is stored exactly as provided.

Implications : if your application runs in multiple time zones or the server/client time zone may change, you must handle timezone conversion in the application layer, otherwise displayed times can become inconsistent. TIMESTAMP is timezone‑aware. MySQL converts the input from the session time zone to UTC for storage and converts it back to the session time zone on retrieval.

This automatic conversion is useful for globally distributed applications, but it adds a small overhead during reads and writes.

Example table and data manipulation:

CREATE TABLE `time_zone_test` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `date_time` datetime DEFAULT NULL,
  `time_stamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

INSERT INTO time_zone_test(date_time,time_stamp) VALUES (NOW(), NOW());

SELECT date_time, time_stamp FROM time_zone_test;

Result (session time zone UTC+0):

+---------------------+---------------------+
| date_time           | time_stamp          |
+---------------------+---------------------+
| 2020-01-11 09:53:32 | 2020-01-11 09:53:32 |
+---------------------+---------------------+

After changing the session time zone to UTC+8:

SET time_zone = '+8:00';

SELECT date_time, time_stamp FROM time_zone_test;

+---------------------+---------------------+
| date_time           | time_stamp          |
+---------------------+---------------------+
| 2020-01-11 09:53:32 | 2020-01-11 17:53:32 |
+---------------------+---------------------+

MySQL time‑zone commands:

# Show current session time zone
SELECT @@session.time_zone;
# Set session time zone
SET time_zone = 'Europe/Helsinki';
SET time_zone = '+00:00';
# Show global time zone
SELECT @@global.time_zone;
# Set global time zone
SET GLOBAL time_zone = '+8:00';
SET GLOBAL time_zone = 'Europe/Helsinki';

Storage space

MySQL date type storage requirements (official documentation):

Before MySQL 5.6.4, DATETIME occupies 8 bytes and TIMESTAMP occupies 4 bytes. Since 5.6.4 they use variable storage (DATETIME 5‑8 bytes, TIMESTAMP 4‑7 bytes) depending on fractional seconds precision.

Range

DATETIME

supports "1000‑01‑01 00:00:00.000000" to "9999‑12‑31 23:59:59.999999" and has no timezone. TIMESTAMP supports "1970‑01‑01 00:00:01.000000" UTC to "2038‑01‑19 03:14:07.999999" UTC and includes timezone conversion.

Performance

Because TIMESTAMP performs UTC↔session‑zone conversion, it may add slight overhead in extremely high‑concurrency scenarios. DATETIME avoids this conversion and can be marginally faster.

Best practice: let the application manage time zones explicitly or set the session time_zone parameter, rather than relying on server defaults.

Are numeric timestamps better?

Many developers store Unix timestamps in INT or BIGINT. This offers the same advantages as TIMESTAMP (efficient sorting, cross‑system compatibility) but sacrifices human readability.

A timestamp is the number of seconds since the epoch (1970‑01‑01 00:00:00 +00:00). It is absolute and timezone‑agnostic, making transmission simple; conversion to local time is done only for display.

Conversion examples:

SELECT UNIX_TIMESTAMP('2020-01-11 09:53:32');
-- returns 1578707612
SELECT FROM_UNIXTIME(1578707612);
-- returns 2020-01-11 09:53:32

PostgreSQL has no DATETIME

PostgreSQL uses TIMESTAMP WITHOUT TIME ZONE (equivalent to MySQL DATETIME) and TIMESTAMP WITH TIME ZONE (equivalent to MySQL TIMESTAMP).

For most applications that need precise event timestamps, TIMESTAMPTZ is the recommended PostgreSQL choice because it handles time‑zone complexities robustly.

Summary

Choosing the right MySQL time storage depends on your requirements: TIMESTAMP is ideal when you need built‑in time‑zone handling and can accept its 2038‑year limit. DATETIME is safer for applications that manage time zones themselves or need dates beyond 2038.

Numeric Unix timestamps give the best performance and cross‑system portability but sacrifice readability.

Each option has trade‑offs; select the one that aligns with your project's needs.