Southsoftware.com - Power tools for home and business users.

WebTweakTools.NET - Web site tweaking software.

more links...

This schedule type allows running tasks once on specified date and time. Since the task will be run only if Advanced Task Scheduler was running before that moment, you can use the option Run task on startup if the time is past the scheduled time while the date is on the specified date to run the task on Advanced Task Scheduler startup if it will be started later on the selected day.