1931 The Japanese military stages the Mukden Incident, an explosion blamed on Chinese dissidents and used as a pretext for the Japanese invasion of Manchuria; World War II started sooner for these two countries.

1930- In january, the Moon moves into its nearest point to Earth, called perigee, at the same time as its fullest phase of the Lunar Cycle. This is the closest moon distance at 356,397 km (221,455 mi) in recent history, and the next one will be on January 1, 2257, at 356,371 km (221,439 mi).

copy pasted from wikipedia, pretty cool fact!

1929 - Sell! Sell! Sell! Holy crap the market is tanking! Sell faster!!

1928 - Invest! Invest! Invest! The market will keep booming forever!

1927... while not a prime number, it is the result of multiplying two prime numbers together.

1926 - Emperor Hirohito ascends the throne in Japan, the second of the three axis powers is now in control of their nation.

1925 - The Geneva Protocol is signed into international law.

1924- the very first Olympic Winter Games were held at the foot of Mont Blanc in Chamonix.

July 1923 – Hyperinflation in the Weimar Republic (Germany) sees the number of marks needed to purchase a single American dollar reach 353,000 – more than 200 times the amount needed at the start of the year.

1922 After their victory in the front of Afion Karahissar, Turkish forces invade Smyrna. Hundreds of women are raped, children killed or mutilated, and thousands are killed trying to escape the burning city.
No word of apology had been ever uttered by any Turkish government,

1921 might appear to be a prime number at first, but it is actually equal to 17x113.

In 1920 there was a great flood in China of the Yellow River, one of the lifeblood of China and one of the biggest floods ever recorded. The Jishi Gorge Dam was built to control the river, however, after several months of the water continuing to rise, the dam broke. At its highest level, it was 240 meters above today's water level :O
Did I mention its 1920 BC!! Crazy how much we know about an ancient flood

The Covenant of the League of Nations is signed on 28 June 1919, probably biggest leap forward that humanity has ever taken.

On the eleventh hour of the eleventh day of the eleventh month, 1918, the Great War ends. Being the "War to End All Wars", this was definitely the ultimate peace treaty and no war has happened since then.

On April 3, [b]1917[/b], Vladimir Ilyich Ulyanov, after hearing that his mother country had just overthrown its monarchy and deciding to make a deal with the Germans to spy on the new government for them in exchange to safe passage to said country, got off a train at Finland Station in Petrograd, Russia.

The rest, obviously, is history.

1916 Easter Rising in Dublin

In The White War ([b]1915[/b]-1918) is the name given to the fighting in the high-altitude Alpine sector of the Italian front during the First World War, principally in the Dolomites, the Ortles-Cevedale Alps and the Adamello-Presanella Alps. More than two-thirds of this conflict zone lies at an altitude above 2,000m, rising to 3905m at Mount Ortler. In 1917 New York World correspondent E. Alexander Powell wrote: “On no front, not on the sun-scorched plains of Mesopotamia, nor in the frozen Mazurian marshes, nor in the blood-soaked mud of Flanders, does the fighting man lead so arduous an existence as up here on the roof of the world.”

On of the most dramatic events was the White Friday (1916). The most significant avalanche struck the Austro-Hungarian barracks on Mount Marmolada, killing 270 soldiers. Other avalanches on the same day would strike Italian and other Austro-Hungarian positions, killing hundreds. According to some reports, both sides deliberately fired shells into the weakened snowpacks in an attempt to bury the other side.

1914 Archduke Franz Ferdinand is assassinated after a 3rd lucky attempt succeeds, creating the sparks that ignited Europe in the fires of war.

1913-Us government ratifies the 16th amendment, allowing the government to impose and collect income taxes on all sources of income, not just some.

Thanks 16th amendment, now we have more taxes >:(

1912 - iceberg sinks big boat