This is a list of selected December 18 anniversaries that appear in the "On this day" section of the Main Page. To suggest a new item, in most cases, you can be bold and edit this page. Please read the selected anniversaries guidelines before making your edit. However, if your addition might be controversial or on a day that is or will soon be on the Main Page, please post your suggestion on the talk page instead.
Please note that the events listed on the Main Page are chosen based more on relative article quality and to maintain a mix of topics, not based solely on how important or significant their subjects are. Only four to five events are posted at a time and thus not everything that is "most important and significant" can be listed. In addition, an event is generally not posted this year if it is also the subject of the scheduled featured article or picture of the day.
To report an error when this appears on the Main Page, see Main Page errors. Please remember that this list defers to the supporting articles, so it is best to achieve consensus and make any necessary changes there first.
December 18: Islamic New Year (2009, 1431 AH); Mourning of Muharram in Shia Islam begins (2009); Republic Day in Niger (1958)
- 1271 – Mongol ruler Kublai Khan established the Yuan Dynasty in present-day Mongolia and China.
- 1892 – The first performance of the fairy tale-ballet The Nutcracker, composed by Pyotr Ilyich Tchaikovsky and based on the story by E. T. A. Hoffmann, was held at the Mariinsky Theatre in Saint Petersburg, Russia.
- 1912 – The Piltdown Man: At a meeting of the Geological Society of London, amateur British archaeologist Charles Dawson claimed that he had been given a fragment of a skull that was discovered at a gravel pit near Uckfield, East Sussex, England, which later turned out to be a forgery.
- 1966 – Epimetheus (pictured), one of the moons of Saturn, was discovered, but was mistaken as Janus. It took 12 years to determine that they are two distinct objects sharing the same orbit.
- 1972 – Vietnam War: A few days after peace talks collapsed, the United States began Operation Linebacker II against North Vietnam, the largest heavy bomber strikes launched by the U.S. Air Force since the end of World War II.