This is a complete misrepresentation of history. The amount of time they had to work was usually uncompensated (financially) time that they worked for their lord or their church. It was compulsory, and failing to meet your obligations for any reason *could* get you kicked off your land. 


The other half of the year, that people assume was vacation time, was time spent keeping themselves alive. They didn't have a convenient gas line for cooking or heating their homes, they had to chop wood to keep themselves fed and warm. They had to engage in growing their own food, and subsistence farming is HARD WORK. Whatever they could grow beyond their needs was sent to markets so they could buy cloth to sew their own clothes. 


Trust me, some people love to claim that we have it so bad compared to peasants, but they wouldnt last a year as a peasant. 