// from any read operation.)
func (b *Buffer) UnreadRune() error {
	if b.lastRead <= opInvalid {
		return errors.New("bytes.Buffer: UnreadRune: previous operation was not a successful ReadRune")
	}
	if b.off >= int(b.lastRead) {
		b.off -= int(b.lastRead)
	}
	b.lastRead = opInvalid
	return nil
}

            var lastDay = moment([year, month, daysInMonth]);
            var lastMonth = moment(firstDay).subtract(1, 'month').month();
            var lastYear = moment(firstDay).subtract(1, 'month').year();
            var daysInLastMonth = moment([lastYear, lastMonth]).daysInMonth();
            var dayOfWeek = firstDay.day();

            //initialize a 6 rows x 7 columns array for the calendar
            var calendar = [];