DWF3046 writes "There are lots of things you can infer from Twitter. But while we're learning what we're eating or where we're flying, we haven't been able to use Twitter to determine how we're feeling. Researchers at Harvard and Northwestern have created a video that shows the mood in the US, as inferred using over 300 million tweets, over the course of the day. The results? The early morning and late evening appear to provide the highest levels of happiness. Geographically, the data points to a significantly happier west coast, which is consistently three hours behind the east coast."