Suppose the column in your table (called 'my_table') is called 'my_date', try this:
SELECT my_date, CURDATE() - my_date
FROM my_table
This will give you the difference, in days, between today's date, and the date stored in my_date, negative being in the future.
If the column is a DATETIME column, replace CURDATE() with NOW(), and your results will be in seconds.