April Fool's Day in Swedish History
It’s been said that the origins of April Fools' Day stem from the Roman festival of Hilaria, which in reality was held on March 25, and the Medieval Feast of the Fools, which was held on December 28. Be that as it may, April Fools’ Day (Första April in Swedish) is celebrated in many countries, though it is not a national holiday it is a day when people are allowed to play practical jokes and hoaxes on each other. In Swedish there’s a rhyme that goes: “April, april din dumma sill, jag kan lura dig vart jag vill” (April, April you silly herring, I can fool you anywhere I want to), which concludes a successful practical joke.

Last year's best Swedish joke may have been "Power Outage at Skansen - over 130 animals, including monkeys, zebras and bears roaming Stockholm inner city streets ..."

Best global joke in 2014 (an one of the best ever) was the new scentsation in search - GOOGLE Nose. Smelling is believing; http://www.google.com/landing/nose/ and, in Sweden, a commercial by Swedish supermarket chain ICA; Say Hello to the ICA Glasses! (In Swedish)

Some of the more famous April first jokes in Swedish media are the following:

1950: On April 1, 1950, the Swedish newspaper Göteborgs-Posten (GP) reports that the island of Öland has loosened from the ocean bed and is floating towards the Swedish coast.

1962: Before there was such a thing as color TV in Sweden, Kjell Stensson explained, during a news segment on TV, that new equipment had been installed in the TV-building, which meant there was no need to buy a new TV in order to view programs in color. It was enough, Stensson said, to pull a nylon stocking over the TV screen.

1980: Daily newspaper DN reports on April 1 in 1980, that daylight savings time (“sommartid” in Swedish) has been introduced on the sly, without prior notice: All watches and clocks were currently wrong, nobody knew exactly what time it was and there was, according to DN, total chaos everywhere. In reality, daylight savings time was introduced on April 6 that same year, the first time for Sweden since 1917.

If you fail to trick someone on April first, you can always try again a month later on May first (although this is not as common a day for jokes). If you succeed to trick the person in question then you say: “Maj, maj måne jag kan lura dig till Skåne” (May, May moon, I can trick you to Skåne).