Which month of Modern Gregorian Calendar was original known as Sextilis?

It was August. It was sixth month of the original 10 month Roman calendar under Romulus in 753 BC. At that time March was the first month of the Roman Calendar. Around 700 BC January & February were added to the Calendar and thus became the eighth month of the calendar. King Numa Pompilius added the January & February. August was given 29 days. In Julian Calendar which was created by Julius Caesar in 45 BC, added two more days in August and thus it came in the form of modern 31 days month. However, in 8 BC it was renamed in the honor of First Roman King Augustus. The names remaining months remained unchanged.