Library.

“In medieval Europe, there were roughly 80 to 100 feast days per year on which work generally stopped.”

The core point holds: medieval Europe had many religious holidays on which ordinary work was often restricted. But 80–100 is not a fixed Europe-wide number; it is a rough estimate that varies by region, century, and counting method, with credible figures both below and above that range. Treat it as an approximation, not a settled annual total.

“During the Middle Ages, scholars thought the Earth was round.”

Historical evidence shows medieval scholars generally regarded Earth as spherical. Primary texts and standard scholastic teaching support that conclusion, especially in Latin Christian and university contexts. The common idea that medieval thinkers believed in a flat Earth is largely a later myth and often confuses popular belief with learned scholarship.

“The invention of the internet influenced the practice of diplomacy during the medieval period.”

The internet could not have influenced medieval diplomacy because it did not exist during the medieval period. The medieval era is conventionally dated to roughly 500–1500, while the internet originated with ARPANET in 1969 — a gap of nearly five centuries. Every authoritative source consulted places internet-driven diplomatic change in the modern era, and no credible evidence supports backward causation or "retroactive influence" on historical practice.