getDateKeyFromDate (date) {
		// get our runtime timezone offset
		const nowDiff = CalendarFetcherUtils.getTimezoneOffsetFromTimezone(moment.tz.guess());
		let startday = date.getDate();
		let adjustment = 0;
		Log.debug(" day of month=", (`0${startday}`).slice(-2), " nowDiff=", nowDiff, ` start time=${date.toString().split(" ")[4].slice(0, 2)}`);
		Log.debug("date string=    ", date.toString());
		Log.debug("date iso string ", date.toISOString());
		// if the dates are different
		if (date.toString().slice(8, 10) < date.toISOString().slice(8, 10)) {
			startday = date.toString().slice(8, 10);
			Log.debug("< ", startday);
		} else { // tostring is more
			if (date.toString().slice(8, 10) > date.toISOString().slice(8, 10)) {
				startday = date.toISOString().slice(8, 10);
				Log.debug("> ", startday);
			}
		}
		return date.toISOString().substring(0, 8) + (`0${startday}`).slice(-2);
	}
get the exdate/recurrence hash key from the date object
BEFORE calling rrule.between
@param the date of the event
@returns string date key YYYY-MM-DD