{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "Customizing time scale domain.",
  "background": "white",
  "padding": 5,
  "width": 200,
  "height": 200,
  "style": "cell",
  "data": [
    {
      "name": "source_0",
      "values": [
        {"a": "December 17, 1995 03:00:00", "b": 28},
        {"a": "December 17, 1995 09:00:00", "b": 30},
        {"a": "December 17, 1995 15:00:00", "b": 30}
      ]
    },
    {
      "name": "data_0",
      "source": "source_0",
      "transform": [
        {"type": "formula", "expr": "toDate(datum[\"a\"])", "as": "a"},
        {
          "field": "a",
          "type": "timeunit",
          "units": ["hours"],
          "as": ["hours_a", "hours_a_end"]
        },
        {
          "type": "stack",
          "groupby": ["hours_a"],
          "field": "b",
          "sort": {"field": [], "order": []},
          "as": ["b_start", "b_end"],
          "offset": "zero"
        },
        {
          "type": "filter",
          "expr": "(isDate(datum[\"hours_a\"]) || (isValid(datum[\"hours_a\"]) && isFinite(+datum[\"hours_a\"]))) && isValid(datum[\"b\"]) && isFinite(+datum[\"b\"])"
        }
      ]
    }
  ],
  "marks": [
    {
      "name": "marks",
      "type": "rect",
      "style": ["bar"],
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "bar"},
          "description": {
            "signal": "\"a (hours): \" + (timeFormat(datum[\"hours_a\"], timeUnitSpecifier([\"hours\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"}))) + \"; b: \" + (format(datum[\"b\"], \"\"))"
          },
          "x2": {"scale": "x", "field": "hours_a", "offset": 1},
          "x": {"scale": "x", "field": "hours_a_end"},
          "y": {"scale": "y", "field": "b_end"},
          "y2": {"scale": "y", "field": "b_start"}
        }
      }
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "time",
      "domain": {
        "fields": [
          {"signal": "{data: datetime(2012, 0, 1, 0, 0, 0, 0)}"},
          {"signal": "{data: datetime(2012, 0, 1, 24, 0, 0, 0)}"}
        ]
      },
      "range": [0, {"signal": "width"}]
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {"data": "data_0", "fields": ["b_start", "b_end"]},
      "range": [{"signal": "height"}, 0],
      "nice": true,
      "zero": true
    }
  ],
  "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "gridScale": "y",
      "grid": true,
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "a (hours)",
      "format": {
        "signal": "timeUnitSpecifier([\"hours\"], {\"year-month\":\"%b %Y \",\"year-month-date\":\"%b %d, %Y \"})"
      },
      "labelFlush": true,
      "labelOverlap": true,
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "b",
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ]
}