title: Amazon Alexa: AMAZON.DATE to Java Date/Duration
body: <p>If I use AMAZON.DATE as a slot type, the user is able to input all kind of dates. Stating from the documentation:
  "2015-12", "2017-WI" (for winter of 2017) or "2015-W48-WE" (for weekend of week 48 of 2015). I want to parse these dates into Java dates/durations and I wonder how to achieve this. </p>
  
  <p>Is there a Java library that takes a date like "2015-12" and returns two dates or a date and a duration?
  I can see a lot of potential problems like time zone handling or ambiguous dates, but I hope this is a common problem.</p>
  
  <p>I could write a parser to save it as two Dates, one for the beginning of the month and one for the end of the month. Or a date for the beginning and a duration, but this seems like a lot of overhead to comply with ISO 8601.</p>