I want to check users' subscribed dates for certain period. And send mail to users whose subscription is finishing (ex. reminds two days). I think the best way is using thread and timer to check dates. But I have no idea how to call this function. I don't want to make a separate program or shell. I want to combine this procedure to my django code. I tried to call this function in my settings.py file. But it seems it is not a good idea. It calls the fucntion and creates thread everytime i imported settings.