How to change a job's scheduled run time

Even if you have changed the scheduled time for a job to run (using DA, on the job properties, schedule tab), you will notice the the job continues to run at the old time.
What's wrong? Let's have a look behind the curtains!
The agent_exec pols the a_next_invocation attribute of the dm_job object to determine when the job should run next.
In fact, when you update the job schedule, this attribute is not updated (it is when the job runs). So, you have to update it manually and the 2 options are:

1. API (using DA or other client):
retrieve,c,dm_job where object_name='[JOB_NAME]'
set,c,l,a_next_invocation
04/09/2012 19:00:00
save,c,l
2. DQL:
update dm_job object set a_next_invocation=DATE('04/09/2012 19:00:00','mm/dd/yyyy hh:mi:ss') where object_name='[JOB_NAME]'

If your changes had no effect, perhaps you have to reinitialize the Content Server process (thread). Use the following API command for that:
reinit,c