CX-Supervisor and the Data Log Viewer use UTC (Universal Time Coordinated) for all times connected with Data Logging. This means that when you log data in different time zones, all log files and times will be comparable.

The 'day' or 'month' breaks are also timed in UTC, not local time or from when you started logging. So if you are in New York you are on UTC -5 (EST) so new DLV files will be created at 19:00 in the evening - that is 5 hours before the new day in local time. If you live closer to the Greenwich meridian (0 degrees) UTC the rollover time will be closer to local time.

If you want to use local time, it is better to use 1 hour periods and archive them manually at midnight (or whenever you want). The DLV will join them automatically when you view so 24 files is no different to 1 file as far as the DLV is concerned.