A processor-based personal electronic device (such as a smartphone) uses combinatorial logic to automatically adjust alarms, notifications, reminders, and the like based on data from device event histories, on-board sensors, user-entered data, and similar information. One particular representative embodiment comprises a process for automatically deleting an unneeded reminder. For example, a user may have a personal electronic device that is set to issue a reminder for a meeting in a certain place, on a certain date at a certain time. If location sensors detect that the user is already at the certain place on the certain date at (or reasonably before) the certain time, the now superfluous reminder is automatically cancelled.