{
  "function": "hour",
  "description": "Extract the hour part from a datetime or time, or the number of hours from an interval.",
  "variants": [
  { "variant": "Time variant",
      "variant_description": "Extract the hour part from a time or datetime.",
      "arguments": [ {"arg":"datetime","description":"a time or datetime value"}],
      "examples": [ { "expression":"hour('2012-07-22T13:24:57')", "returns":"13"}] },
      {
      "variant": "Interval variant",
      "variant_description": "Calculate the length in hours of an interval.",
      "arguments": [ {"arg":"interval","description":"interval value to return number of hours from"}],
      "examples": [ { "expression":"hour(tointerval('3 hours'))", "returns":"3"},
                    { "expression":"hour(age('2012-07-22T13:00:00','2012-07-22T10:00:00'))", "returns":"3"},
                    { "expression":"hour(age('2012-01-01','2010-01-01'))", "returns":"17520"}]
  }]
}