I want to get a list of years from `MyModel` instances date attribute. 

This is the way I do this now:

```
dates = MyModel.objects.filter(site=site).dates('date', 'year')
years = [date.year for date in dates]

```

The result looks like:

```
dates = [datetime.date(2004, 2, 1), datetime.date(2005, 3, 1)]
years = [2004, 2005]

```

Is there any simpler way do this? Any help would be appreciated!