title: Trying to understand “PT1H” in a date-time string
body: <p>I'm using the Weather API to pull weather information down as a service for my project.  I'm trying to understand some timezone offsets that I can't seem to find information on.</p>
  
  <p>The URL I'm using is:</p>
  
  <pre><code>https://api.weather.gov/gridpoints/VEF/154,48
  </code></pre>
  
  <p>Here is some sample return values:</p>
  
  <pre><code>"temperature": {
      "sourceUnit": "F",
      "uom": "unit:degC",
      "values": [
          {
              "validTime": "2019-05-11T16:00:00+00:00/PT1H",
              "value": 18.333333333333371
          },
          {
              "validTime": "2019-05-12T04:00:00+00:00/PT2H",
              "value": 16.1111111111112
          },
          {
              "validTime": "2019-05-12T21:00:00+00:00/PT4H",
              "value": 26.666666666666742
          },
          ...
      ]
  }
  </code></pre>
  
  <p>I understand the <strong>PT</strong> means Pacific Timezone.  But I cant seem to find any information on the next to characters like <strong>1H</strong>, <strong>2H</strong>, etc.  </p>
  
  <p>If anyone can advise that would be appreciated - Thanks</p>