From Dahua Wiki
Day/night config switch is invalid.
Possible reason: Device system time is not corresponding to computer time.
- Log into the web interface of the camera. Click on Setup, General and then the date and time option.
- Set time period according to the computer time.
- Synchronize the device time and current PC time by clicking on the sync pc button.
- Log into the web interface of the recorder and confirm date and time is synced correctly.