src/utils/dateInfo.js
function findShallowIntersectingRange(date1, date2) {
  const thisRange = date1.toRange();
  const otherRange = date2.toRange();
  // Start with infinite start and end dates
  let start = null;
  let end = null;
  // This start date exists
  if (thisRange.start) {
    // Use this definite start date if other start date is infinite
    if (!otherRange.start) start = thisRange.start;
    else
      // Otherwise, use the earliest start date
      start =
        thisRange.start < otherRange.start ? thisRange.start : otherRange.start;
    // Other start date exists
  } else if (otherRange.start) {
    // Use other definite start date as this one is infinite
    start = otherRange.start;
  }
  // Assign end date to this one if it is valid
  if (thisRange.end && (!start || thisRange.end >= start)) {
    end = thisRange.end;
  }
  // Assign end date to other one if it is valid and before this one
  if (otherRange.end && (!start || otherRange.end >= start)) {
    if (!end || otherRange.end < end) end = otherRange.end;
  }
  // Return calculated range
  return { start, end };
}
function findShallowIntersectingRange(date1, date2) {
  const thisRange = date1.toRange();
  const otherRange = date2.toRange();
  // Start with infinite start and end dates
  let start = null;
  let end = null;
  // This start date exists
  if (thisRange.start) {
    // Use this definite start date if other start date is infinite
    if (!otherRange.start) start = thisRange.start;
    else
      // Otherwise, use the earliest start date
      start =
        thisRange.start < otherRange.start ? thisRange.start : otherRange.start;
    // Other start date exists
  } else if (otherRange.start) {
    // Use other definite start date as this one is infinite
    start = otherRange.start;
  }
  // Assign end date to this one if it is valid
  if (thisRange.end && (!start || thisRange.end >= start)) {
    end = thisRange.end;
  }
  // Assign end date to other one if it is valid and before this one
  if (otherRange.end && (!start || otherRange.end >= start)) {
    if (!end || otherRange.end < end) end = otherRange.end;
  }
  // Return calculated range
  return { start, end };
}
Returns a date range that intersects two date info objects NOTE: This is a shallow calculation (does not take patterns into account), so this method should only really be called for special conditions where absolute accuracy is not necessarily needed