UPDATE tbluser SET DateField = DATEADD(ss,numOfSeconds,DateField)

Note the first parameter "ss". This shows that you are adding seconds to the date.

Check the docs for more info.

You should look into DATEADD .

DATEADD (datepart , number , date)

or the full update syntax

UPDATE tbl SET YourDateField = DATEADD (ss, 2, YourDateField)

Updated additional answer for Google surfers, 2023. If you're getting syntax errors from the other answers.

Using MySQL version 8+.

UPDATE table_name SET some_datetime_column_name = DATE_ADD(some_datetime_column_name, INTERVAL 10 SECOND) WHERE some_other_column_name = 'something';