The idea was that in the Middle Ages, there were far more religious and feast days than legal holidays today, a lack of work during the winter months when the fields lay barren, and the typical worker would not spend a full eight+ hours every day of the week ending to crops and livestock. Taking an average of 2,000 hours (50 weeks at 40 hours per week) for a 'modern American worker', is the meme I saw utter rubbish, or is there some truth to its claims?
I've previously answered a question on the working hours of medieval smiths that applies to medieval work more generally. To summarise, while medieval workers worked fewer days per year than modern full time employees, the longer days in summer resulted in an average of about 56 hours per week, or about the same number of hours per year.
Additionally, for many who performed piece work or wage labour, work was seasonal and the feast days were often more harmful than helpful, since it made their pay irregular when they were already in a marginal position. And, with crop failures every few years, wars and other catastrophes, it would be wrong to think of medieval peasants or craftsmen having an easier life than modern workers.