New Year's Day is celebrated at different times and in different ways throughout the world. This is because certain countries and religions around the world use different calendars.
Some calendars are based on the movement of the moon, while others are based on the position of the sun. New Year in China for instance is celebrated on a different day each year, because the Chinese base their calendar on the cycle of the moon. Therefore the Chinese New Year can fall anywhere between January and the beginning of February. Religious festivals for New Year which occur on dates other than 1st January include the Jewish Rosh Hashanah festival and the Muslim Al Hijrah festival.
Generally, New Year's Day is celebrated in westernised countries on January 1st. New Year's Day was formerly observed 4000 years ago in 2000 BC in ancient Babylon. Their New Year celebrations would begin on March 23rd (in our calendar) and would last for 11 days. This date was selected because Spring is synonymous with new beginnings. The Romans continued to observe this date until 153 BC, when January 1st was declared New Year's Day.