It is possible that you pressed the START/STOP key for 2 seconds or more when you start recording.
When the START/STOP key is pressed 2 seconds or more, the mode will be manual operation. Therefore, the setting of stop time and date will be cancelled. If set the start time and date to automatically start, press the START/STOP key once less than 2 seconds.
In case the recording even does not stop at the stop time and date which is set, please make contact with Kyoritsu or with your local Kyoritsu distributor.