Thanks very much for your help. Your last post helped a lot. I am coming up with ideas to make my own task tracking plugin. There will be a "duedate" field in each task tiddler, but some due dates will have a repeat setting (like monthly, weekly, etc). I want a way to either modify the due dates of the task tiddlers appropriately, or create a custom filter.
Let's say that you set a task due on November 9th, 2019, and set it to weekly. That task tiddler should then be due every Saturday, for example. I want to either figure out a way to dynamically modify the due date field so that every week the due date field will automatically change the due date field (in this case set it 7 days ahead), or create a custom filter that will just do that math and filter out tiddlers that are due that day.
So for my filter idea, there would be a "current tasks" tiddler. The current tasks tiddler would have a list widget with a filter that would filter out all tasks due on the current day. For normal tasks (tasks without a repeat setting) that would be simple to accomplish with filters. But for the "repeat" tasks I am not sure how to filter those out appropriately. I am going to work on a custom filter that will examine the duedate field and the repeat field in task tiddlers, and then filter the ones out that are due today by doing basic date math on the duedate and with the repeat setting to filter out tiddlers that are due the current day (or month, week, etc).