During the years between the first introduction of the Gregorian calendar in continental Europe and its introduction in Britain, contemporary usage in England started to change. In Britain, 1 January was celebrated as the New Year festival, but the "year starting 25th March was called the Civil or Legal Year, although the phrase Old Style was more commonly used." To reduce misunderstandings about the date, it was normal in parish registers to place a new year heading after 24 March (for example "1661") and another heading from the end of the following December, "1661/62", a form of dual dating to indicate that in the following twelve weeks or so, the year was 1661 Old Style but 1662 New Style. Some more modern sources, often more academic ones (e.g. the History of Parliament) also use the "1661/62" style for the period between 1 January and 24 March for years before the introduction of the New Style calendar in England.