Whether August 27 is a holiday for the stock market depends on the country and the year in question. Generally, August 27 is not a standard public or market holiday for major stock exchanges such as the New York Stock Exchange (NYSE), NASDAQ, London Stock Exchange (LSE), or Indian stock exchanges like NSE and BSE.
If you require information for a specific year or a particular exchange, it is recommended to check the official holiday calendar for that exchange or consult their website.