Companies are proud of their ability to issue a dividend and will typically have this information available to shareholders and prospective investors on their website, probably in an area called “Investor Relations” or something similar. In addition, many financial websites will have ex-dividend calendars that will provide a list of all announced ex-dividend dates.
This is an easy way for investors to see not only the ex-dividend date of a company they may be interested in buying, but a comparison of dividend amounts for similar companies. Once the ex-dividend date arrives you’ll see an X next to the stock symbol to indicate that it is trading ex-dividend.