The date is averaged over 15 minute intervals.
You can select the frequency band (such as ISM, UNI-1, UNI-2, UNI-3, UNI-4) and the time interval from the top-right corner of the widget.
Click RF Explorer to view the RF airspace around the AP. For more information, see RF Explorer.
Charts that show information about channels other than the operating channels of the AP show the most accurate information when the AP has a dedicated scanning radio. APs that use background scanning show a snapshot of the network that might have changed since the time of the last scan.