This issue hasn't been addressed in any ArcGIS update and is still present in the current versions of ArcGIS Pro and Desktop.
When you check the option "create outputs for each interval" within a day, the tool outputs a multi-band raster of n bands. In my case, using the following settings for my latitude I get 29 bands.
The output bands are just named Band_1 to Band_29 and there is no way to know the time of each band, one can only guess.
What I do is I check on a solar web calculator the sunrise and sunset times for my location in that particular day. You can calculate this in this website, for instance.
In my case the radiation for that day goes as follows:
- Astronomical twilight: 4:53 to 5:36
- Nautical twilight: 5:36 to 06:15
- Civil twilight: 6:15 to 6:46
- Sunrise: 6:46
- Sunset: 21:08
- Civil twilight: 21:08 to 21:39
- Nautical twilight: 21:39 to 22:17
- Astronomical twilight: 22:17 to 23:00
It would be reasonable to have more bands in the diffuse and global radiation outputs since there is enough radiation when the sun is still below the horizon line during the civil twilight "solar illumination suffices for the human eye to clearly distinguish terrestrial objects". I would expect then to have some measure in the diffuse radiation output.
However, accounting the daylenght + civil twilight would be 15 hours and 24 minutes which would result in 30-31 bands. Daylenght is 14 hours 22 minutes which using a half-hour interval is consistent with the 29 resulting bands. Therefore, since sunrise is at 6:46, I assign the first band at 7:00 and the following bands at 7:30, 8:00 and so on. The first band could also start at 6:46 or even at 6:30 so this is still just a guess.