1912 - The passenger liner RMS Titanic sinks at about 2:20 am after hitting an iceberg hours earlier.
1915 - The Armenian Genocide began when the Ottoman Empire undertook the systematic annihilation of Armenian intellectuals and entrepreneurs within the city of Constantinople and later the entire Armenian population of the Empire.
1989 - The Hillsborough disaster, one of the biggest tragedies of Europeanfootball, occurs as Liverpool F.C. fans get involved in a crowd stampede that kills 96 people.
April 15 or, if it falls on the weekend, the following Monday is the deadline for Americans to file their tax returns - post offices across the United States stay open until midnight to accommodate procrastinators
`15' on a bottle of sun lotion is its sun protection factor.
The most common cause of celebration is 15 years of marriage, but almost any event can be celebrated in this way, from the reign of a queen, to 15 successful years of trading by a pickle factory.
But once we reach 15 years there is a gap and the next recognised anniversary is China at 20 years.