Fat Thursday is traditionally observed in the last week of carnival before Lent. The tradition of eating doughnuts on that day in Poland goes back to the 17th century.
Fat Thursday, Polish: tłusty czwartek; is a traditional feast marking the last Thursday before Lent. It is connected with Carnival celebrations. The Lent is a period of fasting so it is the last day before Easter when Poles can cut themselves some slack. The whole day is traditionally dedicated to eating. On that day people usually meet with their friends or relatives and eat large amounts of sweets and other meals that are not eaten during the time of fasting. In Poland most popular sweets served during that special Thursady are of course doughnuts, Polish: pączki.