Hmm, I guess it's that `e` uses localized start-of-week and `d` doesn't:

```js
> moment.lang('fr')
'fr'
> moment().format('d')
'5'
> moment().format('e')
'4'
```

Need to think about how that affects things here. Probably need to pass 0 in instead of `dow` if the user specified `d`.