Usually CCTV DVR Clock time is not correct. If difference is under 24 hour or 1-2day, the real time of a scene on CCTV can be assumed without great effort. But if difference is over a year or a decade, it can't be calculated with calculator or MS Office EXCEL:Because of intercalation.

This app supports investigators and detectives who scan CCTV DVR again and again.
Once you set time difference, this app synchronize two different clock.
If you know real time from a specific CCTV clock time(may differ from real time about many years), set CCTV time on the app, and app would calculate real time taking intercalation.into account.