I still think this should be more specific, sure it is index 7, but why are we using indexing in the first place? We'll forget why in a few months! I suggest something along the lines of:

```
Note: netcdftime.datetime objects return a normal tuple from timetuple(), unlike
datetime.datetime objects which return a named tuple. Index the time tuple (element
7 is day of year) instead of using named element tm_yday.
```
or words to that effect.