Problem: The calendar was a refinement to the Julian calendar amounting to a 0.002% correction in the length of the year. The motivation for the reform was to bring the date for the celebration of Easter to the time of the year in which it was celebrated when it was introduced by the early Church. Because the celebration of Easter was tied to the spring equinox, the Roman Catholic Church considered the steady drift in the date of Easter caused by the year being slightly too long to be undesirable. The reform was adopted initially by the Catholic countries of Europe. Protestants and Eastern Orthodox countries continued to use the traditional Julian calendar and adopted the Gregorian reform after a time, for the sake of convenience in international trade. The last European country to adopt the reform was Greece, in 1923.
What change in date motivated the change in calendars?
The answer is the following: celebration of Easter

Problem: In the early 5th century, the deep crisis suffered by the Roman Empire allowed different tribes of Central Europe (Suebi, Vandals and Alani) to cross the Rhine and penetrate into the rule on 31 December 406. Its progress towards the Iberian Peninsula forced the Roman authorities to establish a treaty (foedus) by which the Suebi would settle peacefully and govern Galicia as imperial allies. So, from 409 Galicia was taken by the Suebi, forming the first medieval kingdom to be created in Europe, in 411, even before the fall of the Roman Empire, being also the first Germanic kingdom to mint coinage in Roman lands. During this period a Briton colony and bishopric (see Mailoc) was established in Northern Galicia (Britonia), probably as foederati and allies of the Suebi. In 585, the Visigothic King Leovigild invaded the Suebic kingdom of Galicia and defeated it, bringing it under Visigoth control.
Which tribe did the Romans subsequently make a treaty with?
The answer is the following: Suebi

Problem: The cuisine of Switzerland is multifaceted. While some dishes such as fondue, raclette or rosti are omnipresent through the country, each region developed its own gastronomy according to the differences of climate and languages. Traditional Swiss cuisine uses ingredients similar to those in other European countries, as well as unique dairy products and cheeses such as Gruyere or Emmental, produced in the valleys of Gruyeres and Emmental. The number of fine-dining establishments is high, particularly in western Switzerland.
What unique dairy cheese is produced in the Swiss valleys of Gruyeres?
The answer is the following: Gruyere

Problem: Under the terms of the concluding Treaty of Versailles signed in 1919, the empire reached its greatest extent with the addition of 1,800,000 square miles (4,700,000 km2) and 13 million new subjects. The colonies of Germany and the Ottoman Empire were distributed to the Allied powers as League of Nations mandates. Britain gained control of Palestine, Transjordan, Iraq, parts of Cameroon and Togo, and Tanganyika. The Dominions themselves also acquired mandates of their own: the Union of South Africa gained South-West Africa (modern-day Namibia), Australia gained German New Guinea, and New Zealand Western Samoa. Nauru was made a combined mandate of Britain and the two Pacific Dominions.
How many people did the Treaty of Versailles add to the British Empire?
The answer is the following:
13 million