If the time on reader is changed by more than one hour, the scan results screen will not show data in the graph that was collected by the Sensor prior to the time change.  A clock icon will show on the display indicating this.  (The data is still logged by the reader and is used in calculations.) On the Daily Graph on the reader, moving forward in time will result in a gap in the graph; moving back in time will result in some data being suppressed.  In both cases, a clock icon will be shown indicating the time change.