your aunt may get a kick our of your country's hero Stone Wall Jackson. He was very religious and held the sabbath in high regard. Unfortunatley sometimes he had to wage war on a Sunday... his solution to this was, as general, to declare another day of the week "the sabbath" that way he could observe the sabbath in honor of the Lord every week. Of course Im sure keeping the calender accurate was hard this way haha.
I dont think it matters what day we worship. As long as we set a day aside for the lord's purposes.