The final solution was adopted 40 years later, in 1582. Upon consulting with the learned astronomers of the time, Pope Gregory XIII issued a proclamation that restored the calendar: "So thus that the Vernal Equinox, which was fixed by the fathers of the Nicene Council at March 21, is replaced on this date, we prescribe and order that there is removed, from October of the year 1582, the ten days which go from the 5th through the 14th inclusively. The day which follows the 4th, when one traditionally celebrates St. Francis of Assisi, shall be the 15th."

In this way, the Equinox once again arrived on March 21, as it had in 325 A.D. To accommodate future drift in the calendar, Gregory made the following provision, "Then, lest the Equinox recede from March 21 in the future, we establish that a bissextile (a.k.a. "leap year") shall be inserted every four years (as with the present custom), except in centennial years....  Thus, the years 1700, 1800 and 1900 will not be bissextile, and then, as with the habit with which we are accustomed, the year 2000 will have a bissextile intercalation day, as the day February 29, and that the same order of intermittent intercalations in each 400 year period will be preserved in perpetuity."

And so Gregory established that three out of four centennial years would not be leap years, so as to drop three days from every 400 years, and thus maintain the predictable order of Easter and the seasons. Remarkably, Gregory looked ahead from the Middle Ages to our lifetimes to establish that the year 2000 would be the first centennial leap year in 400 years. Sadly, our generation is so ignorant of classical astronomy that February 29, 2000 came and went with little or no notice, in the media or otherwise.

Gradual Acceptance

The reformed Gregorian Calendar was immediately adopted in October, 1582 throughout the Roman Catholic nations of Europe. But the Protestant and Eastern Orthodox nations resisted this "popish innovation."

One early Protestant proponent of the new calendar was the astronomer Johannes Kepler. In 1597, he argued with his superiors that it was "small-minded to demonstrate Protestant independence of thought by protesting against a most useful reform introduced by the Catholic Church."

For a century and a half thereafter, the nations of Europe maintained an awkward system of keeping two dates for every notable event, one in the "Old Style" of the Julian Calendar, and another in the "New Style" of the Gregorian Calendar.  For example, one might notice that George Washington's birthday is sometimes given as "February 11, 1732 O.S., February 22, 1732 N.S."

Over time, the Protestant nations gradually accepted the Gregorian Calendar. In 1752, England finally adopted the New Style, and its American colonies followed at the same time. Here's how it was reported in "Poor Richard's Almanack" by "Richard Saunders," a.k.a. Benjamin Franklin: "...the King and Parliament have thought fit to alter our Year, by taking 11 days out of September, 1752, and directing us to begin our Account for the future on the first of January.... wishing withal, according to ancient Custom, that this New Year (which is indeed a New Year, such an one as we never saw before, and shall never see again) may be a happy Year to all my kind Readers."

Nowadays, the Gregorian Calendar has become the civil calendar that regulates the affairs of the entire secular world, including nations far and wide that have no historical Christian roots. 

The Eastern Orthodox Church still retains the Julian Calendar for regulating its church calendar. By the 21st century, the seasons have slipped 13 days from the time of Nicaea. So the Vernal Equinox is now arriving on March 8, O.S. The Eastern Church celebrates Christmas on December 25 as reckoned by the Julian Calendar, which is January 7 on the Gregorian Calendar.

One principle objection of the Eastern Orthodox Church is that the Gregorian Calendar did not reiterate the Nicene prohibition against celebrating Easter after the Jewish Passover. As a matter of fact, we can witness this now in the year 2003. This month, Passover is on April 17, and the Gregorian Easter is on April 20. However, the Orthodox Easter is one week later, on April 27, in accordance with the decree of Nicaea. 

So ironically, 1700 years after the Council of Nicaea established a common celebration of Easter, there is still disagreement over this very issue.


Jay Ryan is a former Contributing Editor to Sky & Telescope magazine. Now he applies all his efforts to the glory of God, especially for the benefit of Christian homeschoolers and other Christian kids. You can drop Jay an email at