Is Dividend Trading As Easy As It Looks?

Having looked at a couple graphs of companies when they pay their dividends, I notice that the stock price rises and falls but not particularly quickly. I would have thought that maybe it is very difficult to buy and sell quickly enough but in fact the rise and fall of the stock price happens over a number of days giving an investor what looks like plenty of time to pull out.

But despite this I doubt it can be that easy? Like you can't be telling me that I can simply buy shares of a company 5 days before the dividend payment, receive say 3% dividend + 3% increase in share price then pull out? What's the catch?

Side Question: When do most companies pay their dividends? Do each of them have their own random dates or is there some specific dates that most companies pay on?