Gridsome's GraphQL Between filter does not work

Question

*I am Japanese. My English is not good, so I translate with Deepl.

I made my blog with Gridsome. I am trying to create a monthly archive page on that blog, but the filter between does not work in PlayGround.

The actual code is as follows (I am trying to get the articles posted in July 2021)

Query

query PostsByDate($periodStartDate: Date, $periodEndDate: Date) {
  years: allPost(filter: {date: {between: [$periodStartDate, $periodEndDate]} }) {
    edges {
      node {
        id
        title
        path
        date(format: "YYYY/MM/DD")
      }
    }
  }
}

Variables

{
  "periodStartDate": "2021-07-01T00:00:00.000Z",
  "periodEndDate": "2021-07-31T23:59:59.999Z"
}

Result

{
  "data": {
    "years": {
      "edges": []
    }
  }
}

An article submitted in July 2021 exists but does not appear in the results. Is there anywhere I am wrong?

PlayGround Image