MySQL Check Time Duration Passed?

MySQL  Time Duration

You may want to check whether a particular date has passed using start date, time duration and current date  when the target date is not physically stored.

For clarity, consider a db table schema as follows.

+-----------+--------------------------+------------------+
| event_id | start_time               | duration_seconds |
+-----------+--------------------------+------------------+
| 005      |'2014-10-1 12:13:08'      | 86400            |
+-----------+--------------------------+------------------+

Here `duration_seconds` is stored using integers. If TIME is used, there 's a limit for 24 hrs.
If you want to get only adverts that have not expired, you will run a query like this.

SELECT * FROM  `events` WHERE TIME_TO_SEC(timediff(now(),start_time))<=`duration_seconds`;