title: filter Graphql result by a Date variable
body: <p>I'm using <code>graphql</code> with <code>gatsby</code> to get data from my DataBase. Below is my query:</p>
  
  <pre><code>export const querymk = graphql`
    query HomePageQuery {
    allMongodbAppsOneapps (
        filter : { my_time: { eq : "2019-08-21T12:35:56.863Z" }}
    )  {
      nodes {
        id
        my_time(formatString: "DD MMMM YYYY")
        text {
          title
          developer
          icon
        }
      }
    }
  }
  `
  </code></pre>
  
  <p>this is working fine.. but i need to replace my filter : <code>eq : "2019-08-21T12:35:56.863Z"</code> by a variable <code>date</code> ( <code>eq : $mydate</code>).. i don't know where to start</p>