This is what I read from Wikipedia about Carnival:

Carnival is a festive season which occurs immediately before Lent; the main events are usually during February. Carnival typically involves a public celebration or parade combining some elements of a circus, mask and public street party. People often dress up or masquerade during the celebrations, which mark an overturning of daily life. In Germany and the Netherlands, the Carnival season is traditionally opened on 11/11 (often at 11:11 a.m.). This dates back to celebrations before the former longer Advent season (40 days now reduced to about four weeks), or with harvest celebrations of St. Martin's Day.

Carnival is traditionally held in areas with a large Catholic and to a lesser extent, Eastern Orthodox makeup. Protestant areas usually do not have Carnival celebrations or have modified traditions, such as the Danish Carnival or other Shrove Tuesday events. Conversely, the Philippines, though a predominantly Roman Catholic country, does not have Carnival celebrations because it has been culturally influenced by neighboring Asian nations, which do not have Carnival celebrations.

We Nigerians do follow unknown cultures and funnily practise the culture in the opposite manner. Calabar is bubbling seriously at the moment and many streets in Lagos are 'maddingly' crazy(this season) with massive loud noise and flames of marijuanas(igbo) every night celebrating what they called Carnival, but you and I clearly know its Street Jams