title: Droid API 22+ options for Date/Duration (in Kotlin)?
body: <p>I'm porting an iOS app to Android, target API 22. I do a bunch of Date/TimeInterval stuff. I do it all in UTC so it just works for me.</p>
  <p>I'm struggling with what to use for Android. There's Date (from the beginning of time, ha ha). I guess I could do duration math by converting to/from the <code>time</code> milliseconds attribute. It's not clear to me what zone/rules apply to those.</p>
  <p>I see people who seem to use Calendars as Date objects and pass those around. That seems a bit off.</p>
  <p>And then there's the new Java 8 java.time stuff which looks pretty complete actually (ZonedDateTime, Duration, etc). But that's API 26 and newer. Is there a back port of this that's reliable?</p>
  <p>My needs are pretty basic (I think):</p>
  <ul>
  <li><p>grab &quot;now&quot; time (in UTC)</p>
  </li>
  <li><p>be able to subtract two times and get a time delta</p>
  </li>
  <li><p>be able to subtract a time delta from a time to get a new time</p>
  </li>
  <li><p>be able to add a time delta to a time to get a new time</p>
  </li>
  <li><p>be able to display/stringify times in the current/local time zone</p>
  <p>... and as a bonus</p>
  </li>
  <li><p>easily instantiate given UTC times from something like ISO8601 strings, for unit testing purposes</p>
  </li>
  </ul>