It directly follows the Jewish festival of Sukkot which is celebrated for seven days, and thus Shemini Atzeret is literally the eighth day.

Simchat Torah is a Jewish holiday that celebrates and marks the conclusion of the annual cycle of public Torah readings, and the beginning of a new cycle.

Shemini Atzeret / Simchat Torah will begin the evening of Monday, October 13 and end the evening of Wednesday, October 15.