diffNow(unit = "milliseconds", opts = {}) {
    return this.diff(DateTime.now(), unit, opts);
  }
Return the difference between this DateTime and right now.
See {@link DateTime#diff}
@param {string|string[]} [unit=['milliseconds']] - the unit or units units (such as 'hours' or 'days') to include in the duration
@param {Object} opts - options that affect the creation of the Duration
@param {string} [opts.conversionAccuracy='casual'] - the conversion system to use
@return {Duration}