title: Java 8: how to derive a ZoneId from ZoneOffset
body: <p>I was reading the <a href="https://docs.oracle.com/javase/8/docs/api/java/time/ZoneId.html" rel="noreferrer">API for the <code>ZoneId</code></a> class. It states that there are three tipes of ID:</p>
  
  <ol>
  <li>derived from ZoneOffset</li>
  <li><p>offset-style IDs with some form of prefix. Examples:</p>
  
  <pre><code>ZoneId.of("GMT+2");
  ZoneId.of("UTC");
  ZoneId.of("UT+01:00");
  </code></pre></li>
  <li><p>region-based. Examples:</p>
  
  <pre><code>ZoneId.of("Asia/Aden");
  ZoneId.of("Etc/GMT+9");
  ZoneId.of("Asia/Aqtau");
  </code></pre></li>
  </ol>
  
  <p>But what is the right syntax for the first kind? Documentation says that </p>
  
  <blockquote>
    <p><em>[ID from ZoneOffset] consists of 'Z' and IDs starting with '+' or '-'.</em></p>
  </blockquote>
  
  <p>What's the combination of String and <code>ZoneOffset</code> object I'm supposed to use to create a <code>ZoneId</code> of the first kind?</p>