Monday, August 31, 2020, is the ex-date and likely the most important for investors. This is the first day post-split shares of both TSLA & AAPL will begin trading and when shareholders should receive their new shares. New shares should be visible in accounts by the 9:30 AM market open on this day.
Friday, August 28, 2020, is the payable date. You must own shares of AAPL or TSLA at the close on this date in order to receive the post-split shares.
August 24, 2020, is the record date. This date is important for the issuer and transfer agent but has little impact on investors.