As nations the world over convene to celebrate the new year, one might assume a single calendar has bound them forever. History, however, reveals a different story. If one studies the pasts of these countries, one finds a variety of different calendars often calibrated to local geographical phenomena and religious revelations. In fact, it was not until the rise of the Roman Empire that the west moved towards a universal system for organizing time.
In 45 B.C Julius Caesar introduced the Julian calendar. Although remarkably accurate for its time, the calendar slowly misaligned with the changing of the seasons. This proved especially problematic during the Christian era, as the time of Easter gradually drifted into different seasons.
Responding to the plea of the faithful, Pope Gregory the XIII introduced the Gregorian calendar in 1582. Although not without its quirks, the new calendar, based on solar patterns, proved both accurate and universally relevant. Using the broad influence of the Catholic Church, Gregory implemented it throughout much of the Christendom. Unfortunately, due to political and religious conflicts, the calendar did not receive widespread acceptance until many years after its inauguration. To read more about the Gregorian calendar check out this article and to view the history of Gregory XIII and his calendar head to Science Source.