New Year's Eve is the last day of the year and the day before New Year’s Day, which marks the start of a new year according to the Gregorian calendar. Pope Gregory XIII introduced the Gregorian calendar in 1582. It was adopted immediately in some areas of Europe but it was not used in various countries until even centuries later. For example, the United Kingdom and the United States started observing the Gregorian calendar in 1752, in which 11 days were dropped.
New Year’s Eve festivities can be traced back to celebrations in Europe that date back before Christianity spread. When many inhabitants in Europe were converted to Christianity, these festivals were merged with Christian beliefs and in time came to mark holidays such as the New Year’s Eve and New Year celebrations.
It is important to note that not all cultures follow the Gregorian calendar in observing New Year’s Eve and New Year’s Day. For example the New Year in the Hindu, Chinese, Coptic, Jewish, Islamic calendars differ to that of the Gregorian calendar.