Are the Genesis days 'ages'?

In an effort to make the Genesis text fit geological time it has been proposed by numerous people that the 6 days of creation are in fact a description of 6 ages, or long periods of time.

I don't think this is correct. The use of 'evening' and 'morning' to describe the extremities of each day signal to me that they are literal days that are being described.

But the argument comes back that the Hebrew word yom, that is translated 'day', is in other parts of scripture used to describe a period of time. This happens in expressions like 'in that day' where the writer is clearly pointing to a lengthy period of time much greater than 24 hours.

This may be true but the problem is that here yom is being used ias part of an idiomatic expression. If we remove the single word out of the whole phrase then it no longer still caries the whole phrase's meaning. For example, take the phrase "Watford played a long ball game". Here 'ball' is being used as part of an expression that means a type of pass in football. But if we take the word out of that context it is no longer correct to define ball as meaning pass. If it did then to say "Pass me the ball" would be a bit of a strange request.

This problem arises from trying to take a passage that was never intended to be a literal description of natural history and make it fit such a chronology.