Syntax:
UNIX_TIMESTAMP(), UNIX_TIMESTAMP(date)

If called with no argument, returns a Unix timestamp (seconds since
'1970-01-01 00:00:00' UTC) as an unsigned integer. If UNIX_TIMESTAMP()
is called with a date argument, it returns the value of the argument as
seconds since '1970-01-01 00:00:00' UTC. date may be a DATE string, a
DATETIME string, a TIMESTAMP, or a number in the format YYMMDD or
YYYYMMDD. The server interprets date as a value in the current time
zone and converts it to an internal value in UTC. Clients can set their
time zone as described in
https://mariadb.com/kb/en/time-zones/.

URL: https://mariadb.com/kb/en/unix_timestamp/

