I think they had Sundays off for religious reasons, but not sure how much choice peasants or farmers had given fields need clearing, seeds need planting, crops needed harvesting and animals needed caring, reproducing, feeding, butchering and preserving, irrespective of day of week.

Slacking on any of the above could result in starvation the coming Winter as well as possibly losing your animals as well. There was lots of interdependencies which were quite unforgiving.

I guess it depends on the era or region of Europe, but it seems "Sabbath-keeping" was not always assumed - it having Jewish connotations.

So it seems that outside of religious holidays, people could have been expected to work every day.

In Catholic Europe it was culturally enforced apart from exceptional situations (like you have to harvest your grain and rain is coming). Sabbath literally means "Saturday" in many central-European languages, so celebrating on Sundays had no Jewish associations. In fact it was the opposite because Jews didn't observed Sundays, so you could be called "a Jew" for not observing Catholic holidays including Sundays.

Feeding animals didn't counted as work, just like nowadays people don't think cooking for your family or brushing your teeth is work.