UTC date labels do not display properly, seem to be using local browser timezone

[mjtribble]

Date labels are shifted one day when viewed in mountain time. Updating browser timezone to UTC shows correct labels

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{
  "data": {
    "format": {
      "type": "csv"
    },
    "values": "dt,value\n2021-10-09,450.0,\n2021-10-10,0.0,\n2021-10-11,410.0,\n"
  },
  "mark": {
    "tooltip": true,
    "type": "bar",
    "line": {
      "color": "darkgreen"
    },
    "point": false
  },
  "encoding": {
    "x": {
      "field": "dt",
      "timeUnit": "utcyearmonthdate",
      "title": "Day",
      "type": "ordinal",
      "axis": {
        "grid": false,
        "labelAngle": 0,
        "labelFont": "AgrilystApercu",
        "format": "%b %d",
        "ticks": true,
        "labelPadding": 6,
        "titlePadding": 15
      }
    },
    "y": {
      "field": "value",
      "type": "quantitative",
      "title": "count",
      "axis": {
        "grid": true,
        "domainColor": "white"
      }
    },
    "color": {
      "value": "#5391f5"
    },
    "opacity": {
      "value": 0.4
    }
  }
}

[domoritz]

Simplified example: Open the Chart in the Vega Editor

[domoritz]

This issue looks a lot like #4044.

I wonder whether we changed something in #5780. @haldenl @kanitw do you see what's wrong here?

[domoritz]

I think formatType on the y-axis should be utc but it's time.

[domoritz]

#7815 fixes the issue.

[AndrewRybka]

The same issue affects the labels of nominal fields:

Open the Chart in the Vega Editor

Is it possible to add support for formatType: "utc" which is supported by Vega?

[domoritz]

I don't see an issue with that. Can you send a pull request?

[AndrewRybka]

@domoritz Sure. Here it is: #9265