Happiness to me is a feeling in time, it could last for an hour or a few days depending on the stimuli.
Contentment is one of those things that to me sounds like it's the preferred outcome, but really it's not for me. I can think particularly on a few ocassions in my life where I've thought I was so content, but it was only my perception of things at that time. I think the more you think you are content, the less you strive for happiness...at least that's how it works for me.