getLanguageTag() {
			function fallback() {
				let oLanguageTag = new LanguageTag(Localization.getLanguage());
				// if any user settings have been defined, add the private use subtag "sapufmt"
				if (!isEmptyObject(mSettings)
						|| Formatting.getCalendarWeekNumbering() !== CalendarWeekNumbering.Default) {
					let l = oLanguageTag.toString();
					if ( l.indexOf("-x-") < 0 ) {
						l += "-x-sapufmt";
					} else if ( l.indexOf("-sapufmt") <= l.indexOf("-x-") ) {
						l += "-sapufmt";
					}
					oLanguageTag = new LanguageTag(l);
				}
				return oLanguageTag;
			}
			return oWritableConfig.get({
				name: "sapUiFormatLocale",
				type: function(sFormatLocale) {return new LanguageTag(sFormatLocale);},
				defaultValue: fallback,
				external: true
			});
		}
Returns the LanguageTag to be used for formatting.

If no such LanguageTag has been defined, this method falls back to the language,
see {@link module:sap/base/i18n/Localization.getLanguage Localization.getLanguage()}.

If any user preferences for date, time or number formatting have been set,
and if no format LanguageTag has been specified, then a special private use subtag
is added to the LanguageTag, indicating to the framework that these user preferences
should be applied.

@returns {module:sap/base/i18n/LanguageTag} the format LanguageTag
@public
@since 1.120