April Fool's Day is an annual custom on 1 April consisting of practical jokes and hoaxes. Jokesters often expose their actions by shouting "April Fools!" at the recipient. Mass media can be involved in these pranks, which may be revealed as such the following day. The day is not a public holiday in any country except Odesa, Ukraine, where the first of April is an official city holiday. The custom of setting aside a day for playing harmless pranks upon one's neighbor has been relatively common in the world historically.

Origins
A disputed association between 1 April and foolishness is in Geoffrey Chaucer's The Canterbury Tales. In the Nun's Priest's Tale, a vain cock Chauntecleer is tricked by a fox on "Syn March bigan thritty dayes and two", i.e., 32 days since March began, which 1 April. 

Long-Standing Customs
United Kingdom
In the UK, an April Fool prank is sometimes later revealed by shouting "April Fool!" at the recipient, who becomes the "April Fool". A study in the 1950s, by folklorists Iona and Peter Opie, found that in the UK, and in countries whose traditions derived from the UK, the joking ceased at midday. This continues to be practice, with the custom ceasing at noon, after which time it is no longer acceptable to play pranks. Thus a person playing a prank after midday is considered the "April Fool" themselves.

Scotland
In Scotland, April Fool's Day was originally called "Huntigowk Day", although this name seems to have fallen into disuse over the years. The name is a corruption of "hunt the gowk", gowk being Scots for a cuckoo or a foolish person.

Ireland
In Ireland, it was traditional to entrust the victim with an "important letter" to be given to a named person. That person would read the letter, then ask the victim to take it to someone else, and so on. The letter when opened contained the words "send the fool further".

Nordic Countries
Danes, Finns, Icelanders, Norwegians, and Swedes celebrate April Fool's Day. Most news media outlets will publish exactly one false story on 1 April; for newspapers, this will typically be a first-page article but not the top headline.

April Fish
In Italy, France, Belgium, and French-speaking areas of Switzerland and Canada, the 1 April tradition is often known as "April Fish". Possible pranks include attempting to attach a paper fish to the victim's back without being noticed. This fish feature is prominently present on many late 19th to 20th century French April Fools' Day postcards. Many newspapers also spread a false story on April Fish Day, and a subtle reference to a fish is sometimes given as a clue to the fact that it is an April Fool's prank.

Frequently Asked Questions:
Q. Bharat mai April Fool kab se manaya jata hai?
A. Bharat mai April Fool bahut varsho se manaya ja rha hai. Ye zayada tr British India Rule k time se start hua hoga, kyunki bahut saari traditions British log yaha chod gaye.

Q. Can we not prank someone on 2nd April?
A. Anyone who tries to prank someone after the afternoon of 1st April is considered a fool him or herself. This is a tradition, which states that anyone who is made an April Fool should be told before afternoon that he or she has been pranked.

References;
1. April Fool Day