It's not possible to get a value from ezdate fieldtype when using GraphQL.

Steps to reproduce:
1. Login as admin
2. Create a new Content Type named "MyDate"
3. Add ezdate fieldtype
4. Create a Content Item using that Content Type
5. Regenerate GraphQL schema and clear cache
6. Enter following query:

{
  content {
    myDate(locationId: CONTENT_LOCATION_ID)
    {
      newEzdate1 {
        timestamp
        format(pattern: "d")
      }
    }
  }
}

result:
timestamp field causes an error:

      "debugMessage": "Call to undefined method eZ\\Publish\\Core\\FieldType\\Date\\Value::getTimestamp()",
      "message": "Internal server Error",
(...)

format return null - the same query for ezdateandtime fieldtype returns correct values, so something must be wrong with the format option as well (it should return the specified day.