@blockly/field-date

import * as Blockly from 'blockly';
import FieldDate from '@blockly/field-date';

Blockly.Blocks["test_fields_date"] = {
  init: function () {
    this.appendDummyInput()
      .appendField("date: ")
      .appendField(new FieldDate("2020-02-20"), "FIELDNAME");
  }
};

import * as Blockly from 'blockly';
import '@blockly/field-date';

Blockly.defineBlocksWithJsonArray([
    {
        "type": "test_fields_date",
        "message0": "date: %1",
        "args0": [
            {
                "type": "field_date",
                "name": "FIELDNAME",
                "date": "2020-02-20"
            }
        ]
    }]);