Many historians believe the Babylonians were the first to celebrate New Year's Day over four thousand years ago. They observed New Year's Day in late March to coincide with spring's crop planting season. Resolutions are said to be a reflection of the Babylonians' belief that what a person does on the first day of the New Year will have an effect throughout the entire year.
The ancient Romans later officially declared January 1st as the beginning of the new year. In 46 B.C. Roman Dictator Julius Caesar created a new calendar, cementing the date as the start of the new year. The Western world was slow to adopt New Year's Day, mainly because the Catholic Church denounced it as paganism. It wasn't until 1582, that Pope Gregory the Eighth, revised the Western calendar to reflect the Romans version and include January 1st as New Year's Day.
Other cultures do not celebrate New Year's on January 1st. The Chinese New Year doesn't start until between mid-January and mid-February. The reason the 15-day holiday is not set in stone is because the Chinese New Year is a lunar holiday, beginning with the arrival of the second new moon following the winter solstice. The Muslim New Year is also based on movements of the moon. In Iran, people celebrate the New Year in March. The Hindu New Year can either fall in October or January, depending on which variation of Hindu a follower believes. The Vietnamese New Year is called "Tet" for short, and usually falls between January 21st and February 19th. New Year's Day in Japan is, like Western nations, on January 1st.