Researchers analysed more than 509 million posts from 2.4 million users of the micro-blogging website to study trends in their moods over a two-year period. They found that outlook of people varies greatly depending on the time of day, the day of the week and whether the days are getting longer or shorter.
In the morning people wake up full of optimism, but it declines during the day and only recovers after 6 PM when thestresses of work are forgotten. Negative emotions like anger, distress and guilt are lowest at the start of the day but continue to build until we go to bed, the study revealed.
Twitter accounts from 84 different countries across the globe showed the same pattern despite having significant cultural and geographical differences, 'The Daily Telegraph' newspaper reported.
Overall British Twitter users were more optimistic than those in France and Portugal, but less than people in the USA and Australia, scoring slightly below average on a global scale, the findings showed.
On weekends people were generally more positive but the morning surge of optimism arrived two hours later because people enjoyed a lie-in.
Writing in the 'Science' journal, Scott Golder and Prof Michael Macy of Cornell University in America said the positive effects of sleep, along with our natural behavioural cycle known as circadian rhythm, could explain the trend.
They used a text analysis computer program to scour their sample of Twitter messages, or Tweets, to look for words which suggested how the writer was feeling.
Some messages expressed positive feelings such as enthusiasm, delight, activeness and alertness, while others indicated negative emotions like distress, fear, anger, guilt and disgust.
Positive language accounted for about six per cent of all words used at the highest point but dropped to five per cent during working hours while negative messages rose slowly throughout the day.
The researchers also found that people had a brighter outlook when days were lengthening towards the summer solstice, and this fell away as daylight hours grew shorter.