I wish to know more about formatting code. For example, by recording a
macro, I can tell that the code below forces a date to appear a
certain way.

"[$-409]mmmm d, yyyy;@"

By recording, copying, and pasting I am usually able get things to
look the way I want. However, I would like to understand this type of
code a little better.

What does the [$-409} do?
What does mmmm do as opposed to mm, or d as oppossed to dd?
What does ;@ mean?

The above questions are meant to be rhetorical. I would rather know
how to learn this information for myself, since the above code is
merely one example.

Thanks all!