Correct interpration of dates with localized months

Localized months were not recognized as valid inputs of the `aria.utils.Date.interpret` method.
This means that whenever the user selected a date in a DatePicker with output pattern containing "MMM" or "MMMM" (meaning with the localized short or full month), and then just changing, for example, the year, the entry could not be recognized.

This commit adds this feature.