The 'certainty' field is used to state if the 'location' is certain or not. If a location is 'near' some location, then the location can have the closest area to it, possibly a county, or state, if nothing more is known.
In the Biography or Research Notes, is the correct 'placement' for the 'near' location or the 'possibility'. Dates are not supposed to have a 'range' of dates, which would be the same thing in a location as 'near a location'. If you put a date range in a date field, it would come up with an Error / Suggestion, also.