title: What is the allowed syntax for a Github release tag_name?
body: <p>The apps I'm trying to place under version control store their version number as a timestamp...</p>
  
  <p><code>2019-12-28T05:13:47Z</code> . </p>
  
  <p>When I try to add this timestamp as a <a href="https://developer.github.com/v3/repos/releases/#create-a-release" rel="nofollow noreferrer">Github release <code>tag_name</code> using the API</a>...</p>
  
  <pre><code>{
    "tag_name": "2019-12-28T05:13:47Z",
    "target_commitish": "master",
    "name": "2019-12-28T05:13:47Z",
    "body": "LATEST RELEASE",
    "draft": false,
    "prerelease": false
  }
  </code></pre>
  
  <p>I get a status 422 error...</p>
  
  <pre><code>{
    "message": "Validation Failed",
    "errors": [
      {
        "resource": "Release",
        "code": "custom",
        "field": "tag_name",
        "message": "tag_name is not a valid tag"
      },
      {
        "resource": "Release",
        "code": "custom",
        "field": "tag_name",
        "message": "tag_name is not well-formed"
      },
      {
        "resource": "Release",
        "code": "custom",
        "message": "Published releases must have a valid tag"
      }
    ],
    "documentation_url": "https://developer.github.com/v3/repos/releases/#create-a-release"
  }
  </code></pre>
  
  <p>If I change the tag to <code>v1</code> or the like, there is no error. </p>
  
  <p>The API docs do not state a syntax for release <code>tag_name</code>, but apparently there is. Anyone know where its documented?</p>