getCustomIslamicCalendarData() {
			return aCustomIslamicCalendarData?.slice() ?? undefined;
		}
Returns the currently set customizing data for Islamic calendar support.

See: {@link module:sap/base/i18n/Formatting.CustomIslamicCalendarData}

@returns {module:sap/base/i18n/Formatting.CustomIslamicCalendarData[]|undefined} Returns an array that contains the customizing data. Each element in the array has properties: dateFormat, islamicMonthStart, gregDate. For details, please see {@link #.setCustomIslamicCalendarData}
@public
@since 1.120