Genesis 1:5 - Day and Night

It starts to become more and more interesting, the next passage goes like this:

And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.

The first day out of many. And this was the first day. This is open to interpretation, does a Day mean, in fact, a single Day, or is it a metaphor for a period of time? I haven't really been interested in the Bible in the past, but this I have heard debated before. There are those that means that the Earth is 6000 (something) years old, and there are those meaning that the Earth is older, according to science, but that the Bible is still correct, because it's only metaphors.

I haven't got a real conclusion, but this was interesting at least. I found a nice article about it here: How old is the earth according to the bible? Interesting and easy to understand, but I still haven't landed on any conclusion. What about carbon-14?