Masks have always been an important feature of the Venetian carnival. Traditionally people were allowed to wear them between the festival of Santo Stefano (St. Stephen’s Day, December 26) and the end of the carnival season at midnight of Shrove Tuesday. As masks were also allowed on Ascension and from October 5 to Christmas, people could spend a large portion of the year in disguise. Maskmakers (mascherari) enjoyed a special position in society, with their own laws and their own guild.
Source: Carnival of Venice – Wikipedia