If you're an individual stock investor, you may at times buy a stock because it has a fat dividend. After all, that's guaranteed money (although there's no guarantee that the price of the stock won't go down). However, I have to cop to a rookie mistake I just made when it comes to dividends-not paying attention to the ex-dividend date.

If you don't know, here's the deal with dividends. When a company is getting ready to give out its quarterly dividend (assuming it has one), it will announce the size of its dividend, and then say that it will pay out the dividend on a certain day in the future to shareholders on the books as of a certain date. For example, the company I was looking at was offering a dividend of 50 cents or so to be paid on July 22, for all shareholders on record as of June 28th.

I happened to be looking at this stock on June 27th and thought, "Hey, I like the stock and it's about to pay a big dividend." So I bought it-forgetting about that nasty ex-dividend date.

For whatever reason, maybe just to make it more difficut for individual investors to make any money, there is not just a date that you have to be on the books as an investor, there is also a date a couple of days BEFORE that date called the ex-dividend date-this is the REAL date that you have to buy BEFORE if you want the dividend.

So, in my example, the company announced its date that you had to be a shareholder by, but also announced the ex-dividend date of June 26. What that means to me is that because I bought the stock on June 27th, which appears to be the day BEFORE I need to be on the books, it's actually two days AFTER I needed to make the purchase to be on the books. In short, anytime you see that a company is paying a dividend on a certain date, find the ex-dividend date and make sure to buy BEFORE that date if you want the dividend. In my example, the 25th is actually the last day I could've purchased in order to get the dividend.

Once more: In order to get the dividend, the last day you can purchase the stock is the day BEFORE the ex-dividend date.

Why do they do this? Why have an ex-dividend date that is a couple of days before the date that they claim is when you have to be a shareholder of record? I have no freaking idea. Why not just proclaim the very latest date you can buy the stock to get the dividend and leave it that? Why confuse us?

Because they're greedy pigs, that's why. Which is not very Zen of me at all.

[NOTE: I have modified this post based on the helpful feedback I got in the comments, as I think I hadn't made it clear that the last date to purchase is the day BEFORE the ex-dividend date.]