title: how to convert from ZonedDateTime to Joda DateTime
body: <p>I've switched to threeten for date times but I've still got a 3rd party tool that uses joda to write timestamp with timezone to the database and I need to convert from one to the other.
  What's the best way?
  As a workaround I tried DateTime.parse(zdt.toString) but it falls over because joda doesn't like the zone format</p>
  
  <p>Invalid format: "2015-01-25T23:35:07.684Z[Europe/London]" is malformed at "[Europe/London]"</p>