January 1: The Catholic Church influenced many countries in western Europe, during the Middle Ages in order to move the start of the year.

The most important Christian festivals were: December 25 (the Nativity of Jesus), March 1, March 25 (the Annunciation), or even Easter. Eastern European countries (most of them with populations showing allegiance to the Orthodox Church) began their numbered year on September 1 from about 988.

In England, January 1 was celebrated as the New Year festival, but from the 12th century to 1752 the year in England began on March 25 (Lady Day). So, for example, the Parliamentary record notes the execution of Charles I as occurring on January 30, 1648, (as the year did not end until March 24), although modern histories adjust the start of the year to January 1 and record the execution as occurring in 1649.

Most western European countries changed the start of the year to January 1 before they adopted the Gregorian calendar. For example, Scotland changed the start of the Scottish New Year to January 1 in 1600. England, Ireland and the British colonies changed the start of the year to January 1 in 1752. Later that year in September, the Gregorian calendar was introduced throughout Britain and the British colonies. These two reforms were implemented by the Calendar (New Style) Act 1750.

January 1 became the official start of the year as follows:

· 1362 Grand Duchy of Lithuania

· 1522 Republic of Venice

· 1544 Holy Roman Empire (Germany)

· 1556 Spain, Portugal

· 1559 Prussia, Sweden

· 1564 France

· 1576 Southern Netherlands

· 1579 Duchy of Lorraine

· 1583 Dutch Republic (northern)

· 1600 Scotland

· 1700 Russia

· 1721 Tuscany

· 1752 Great Britain (excluding Scotland) and its colonies.

Source: http://en.wikipedia.org/wiki/January_1