I've been reading Ben Willson's The Making of Victorian Values: Decency and Dissent in Britain, 1789-1837 and encountered the following passage describing a custom in this era:
In trades where laborers were relatively free, where industry was small in scale and out-work was common, Monday was a day off, whatever employers wanted. This custom — called "St. Monday" by those for whom it was a sacrosanct holiday — was to be enjoyed in the alehouse or rowdy sports. The first day of the week would be used for checking machinery, running repairs and administration. Productivity was not ruined by this custom: workers fitted six days' worth of work into the remaining five. (p. 87-8)
The "remaining five" working days include Saturday, of course. Saturday only became a day off in the late 19th and early 20th centuries. But I suspect St. Monday is still celebrated somewhat by people who prefer a smoother and less jarring entrance into the work week.