One-Time Triggers allow you to create a Trigger that will fire one time and then delete itself. Simply choose the One-Time Trigger type when adding a Trigger or Task and choose a date. When the date comes due, the Trigger will fire and create a new Task in the Incoming folder, and then the Trigger will delete itself.
This is a great way to get tasks out of sight until they’re due without the danger of forgetting about them.
For example, say you want to call “Joe” on his birthday next Tuesday. Having the task “Call Joe” on your list before next Tuesday is sort of pointless since you can’t do anything with it before that. Instead, change that task to a One-Time Trigger due on Tuesday. When Tuesday rolls around, the “Call Joe” task will appear in your Incoming folder.