Thanks all,
I am currently running FreeRADIUS Version 2.1.12,
mysql version 5.1.73

I have set up counter.conf based on guide from http://lists.freeradius.org/pipermail/freeradius-users/2005-October/003506.html

however, I noticed the counter just keep counting without terminating the user.

my radgroupcheck is as follows:
mysql> select * from radgroupcheck;
+----+-----------+------------------+----+-------+
| id | groupname | attribute        | op | value |
+----+-----------+------------------+----+-------+
|  1 | validity  | Max-Secs-Passed  | := | 300   |
|  2 | validity  | Idle-Timeout     | += | 300   |
|  3 | validity  | Simultaneous-Use | := | 1     |
+----+-----------+------------------+----+-------+
3 rows in set (0.00 sec)

my counter.conf has the following: 
sqlcounter validity {
                counter-name = All-Secs-Passed
                check-name = Max-Secs-Passed
                sqlmod-inst = sql
                key = User-Name
                reset = daily
                query = "SELECT UNIX_TIMESTAMP(now()) - UNIX_TIMESTAMP(AcctStartTime) secs_passed_since_start FROM radacct WHERE UserName = '%{%k}' LIMIT 1"
}

an attribute called validity and I set Max-Secs-Passed to 300.

however, I discover the query is not returning values in secs and I will like the user to spend only an hour a day and reset the counter the following day to zero for another 1 hour everday.

Can someone assists?