How to convert a datetime value into seconds since year 0 using the TO_SECONDS() function?

TO_SECONDS(datetime) is a MySQL built-in function that converts a datetime value into seconds since year 0. For example:

SELECT TO_SECONDS('1995-05-01'), TO_SECONDS(950501);
  -- +--------------------------+--------------------+
  -- | TO_SECONDS('1995-05-01') | TO_SECONDS(950501) |
  -- +--------------------------+--------------------+
  -- |              62966505600 |        62966505600 |
  -- +--------------------------+--------------------+

SELECT TO_SECONDS(NOW()), NOW();
  -- +-------------------+---------------------+
  -- | TO_SECONDS(NOW()) | NOW()               |
  -- +-------------------+---------------------+
  -- |       63867305526 | 2023-11-15 22:12:06 |
  -- +-------------------+---------------------+

Reference information of the TO_SECONDS() function:

TO_SECONDS(datetime): int
  Given a date or datetime expr, returns the number of seconds since
  the year 0. If expr is not a valid date or datetime value, returns NULL.

Arguments, return value and availability:
  datetime: Required. The datetime value to be converted.
  int: Return value. The number of seconds since year 0.
  Available since MySQL 4.

Related MySQL functions:

• TO_DAYS() - Converting Date to Days

⇒ UNIX_TIMESTAMP() - Calculating Unix Timestamp

⇐ TO_DAYS() - Converting Date to Days

⇑ MySQL Functions on Date and Time

⇑⇑ MySQL Function References