checkTimezonesConsistency(sCLDRTag, oTimezoneNames) {
		Timezones.checkTimezoneNames(sCLDRTag, oTimezoneNames);

		const aTimezoneIDs = Timezones.getTimezoneIDs(oTimezoneNames);
		if (this._aLastTimezoneIDs.length !== 0) {
			const aMissingTimezoneIDs = this._aLastTimezoneIDs.filter((sTimezoneId) => {
				return !aTimezoneIDs.includes(sTimezoneId);
			});
			const aUnexpectedTimezoneIDs = aTimezoneIDs.filter((sTimezoneId) => {
				return !this._aLastTimezoneIDs.includes(sTimezoneId);
			});
			if (aMissingTimezoneIDs.length || aUnexpectedTimezoneIDs.length) {
				throw new Error("'" + sCLDRTag + "' has inconsistent time zone IDs; missing IDs: "
					+ aMissingTimezoneIDs + "; unexpected IDs: " + aUnexpectedTimezoneIDs);
			}
		}
		this._aLastTimezoneIDs = aTimezoneIDs;
	}
Checks whether the time zone names are unique and whether the time zone IDs are as expected
and the IDs for the current locale are the same as for the previous locale.

@param {string} sCLDRTag
  The language tag as defined by the IETF BCP 47, e.g. "en", "de-CH" or "sr-Latn"
@param {Object<string, object>} oTimezoneNames
  The resulting <code>timezoneNames</code> object of the currently processed locale
@throws {Error}
  If time zones are inconsistent over all languages, or if there are duplicate time zone names