Feelings of well-being and happiness are important to overall physical and mental health. People with higher well-being are found to live longer, healthier and more successful lives. In most research, well-being is assessed at a single time point. However, like many complex human traits, feelings of well-being fluctuate over the day or week and across contexts. Furthermore, some people show relatively stable levels of well-being over time and across contexts, while others fluctuate a lot. In a genetically informed study, we investigate the individual differences in daily, weekly and seasonal patterns of well-being and the interaction with the social environment in a large sample of twins of the Netherlands Twin Register.