Techniques are disclosed for detecting and resolving conflicts in context information from various sources. That information may be used to automatically update one or more context sources and/or to validate or invalidate (until further notice or for a period of time) input from one or more context sources. Or, the updates can be made in response to the user's instructions. Rules are used in preferred embodiments to dictate the conflict resolution approach for individual users. Updating the context source is particularly useful when the source is an electronic calendar. Updates that may be made to the calendar include adding, deleting, or changing scheduled events and/or working hours. Invalidating data from a context source is particularly useful for lost, forgotten, misplaced, or loaned devices. Marking data from a context source as valid is preferably done when harmony among several context sources is detected. Context suppliers may be notified of errors or discrepancies in their context data.