Live countdown clock with django and sql?
I have also encountered the same problem a while ago.
First of all your problem is not related neither django nor sql. It is a general concept and it is not very easy to implement because of overhead in server.
One solution come into my mind is keeping start time of the process in the database.
When someone request you to see remaingn time, read it from database, subtract the current time and server that time and in your browser initialize your javascript function with that value and countdown like 15 sec. After that do the same operation with AJAX without waiting user's request.
However, there would be other implementations depending your application. If you explain your application in detail there could be other solutions.
For example, if you implement a questionnaire with limited time, then for every answer submit, you should pass the calculated javascript value for that second.
If I make a live countdown clock like ebay, how do I do this with django and sql?  I'm assuming running a function in django or in sql over and over every second to check the time would be horribly inefficient.  
Is this even a plausible strategy?
Or is this the way they do it:
When a page loads, it takes the end datetime from the server and runs a javascript countdown clock against it on the user machine?
If so, how do you do the countdown clock with javascript? And how would I be able to delete/move data once the time limit is over without a user page load? Or is it absolutely necessary for the user to load the page to check the time limit to create an efficient countdown clock?