How to calculate the Unix timestamp from a given datetime value using the UNIX_TIMESTAMP() function?

UNIX_TIMESTAMP(datetime) is a MySQL built-in function that calculates the Unix timestamp from a given datetime value. For example:

SELECT UNIX_TIMESTAMP(), UNIX_TIMESTAMP('2025-11-13 10:20:19.012');
  -- +------------------+-------------------------------------------+
  -- | UNIX_TIMESTAMP() | UNIX_TIMESTAMP('2025-11-13 10:20:19.012') |
  -- +------------------+-------------------------------------------+
  -- |       1700105959 |                            1763047219.012 |
  -- +------------------+-------------------------------------------+

SELECT UNIX_TIMESTAMP('1970-01-01 00:00:00');
  -- +---------------------------------------+
  -- | UNIX_TIMESTAMP('1970-01-01 00:00:00') |
  -- +---------------------------------------+
  -- |                                 18000 |
  -- +---------------------------------------+

SELECT @@system_time_zone, 18000/60/60;
  -- +--------------------+-------------+
  -- | @@system_time_zone | 18000/60/60 |
  -- +--------------------+-------------+
  -- | EST                |  5.00000000 |
  -- +--------------------+-------------+

Reference information of the UNIX_TIMESTAMP() function:

UNIX_TIMESTAMP(datetime): sec
  Returns the value of the argument as seconds since
  '1970-01-01 00:00:00' UTC.

Arguments, return value and availability:
  datetime: Optional. Default is current datetime. The datetime value
    to be converted.
  sec: Return value. The number of seconds between '1970-01-01 00:00:00'
    and the given datetime.
  Available since MySQL 4.

Related MySQL functions:

• FROM_UNIXTIME() - Unix Time to Datetime

⇒ UTC_DATE() - Current UTC Date

⇐ TO_SECONDS() - Converting Datetime to seconds

⇑ MySQL Functions on Date and Time

⇑⇑ MySQL Function References