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Date Distinctions

To the Editors:

I was greatly interested in “The Future of Time,” by David Finkleman and colleagues (July–August). After the authors expound on the extreme accuracies required for timekeeping, involving leap seconds, it is ironic that the only definite date quoted, that of George Washington’s birthday, is out by a whole year.

Geoffrey G. Eichholz
Atlanta, GA

To the Editors:

In “The Future of Time,” the authors state that “different countries and religions adopted the reforms [the Gregorian calendar] at different times and in different ways. In 1712 Sweden added a February 30 to its national calendar.” There was a February 30 in Sweden in 1712, but the context in which it is presented in the article is misleading. In 1700 the Swedes decided to switch from the Julian to the Gregorian calendar by eliminating leap-year days for 40 years. So 1700, which is a Julian leap year but not a Gregorian leap year, did not have a leap day. In both 1704 and 1708, through bureaucratic error, there were leap days. In 1712, the situation was resolved by switching back to the Julian calendar; this meant that the missing leap day that would have occurred in 1700 had to be added, and was, as February 30. It wasn’t until 1753 that the Swedes finally adopted the Gregorian calendar by making the date March 1 follow February 17.

Peter Zilahy Ingerman
Willingboro, NJ

Drs. Finkleman and Seaman respond:

On the matter of George Washington’s birthday, our article is correct, but so is Geoffrey Eichholz. We wrote that “Washington was born on February 11, 1731 O.S. (Old Style). The United States celebrates his birthday each year on February 22 because an 11-day deficit was corrected during his lifetime.” These statements are perhaps not ironic, but incomplete. “Old Style” refers not only to the 11-day adjustment from the Julian to the Gregorian calendar, but also to a change in the observance of New Year’s Day. In England and its colonies, New Year’s Day was on March 25, not January 1. Thus Washington was born on February 11 of 1731—but after the calendar change this date became February 22 of the following year. This complication serves to highlight our observation that “the date of Washington’s birthday on the calendar may be arguable, but the astronomical timing of his birth is not.”

We thank Peter Zilahy Ingerman for expanding upon the history of the Swedish calendar. This example further demonstrates the world’s calendrical diversity. Calendars and clocks are a civil and logistical convenience. Using them to keep track of physical events will always require knowledge of intercalary changes that occurred in the past as well as policies for handling special cases that will inevitably arise in the future.

Duncan Steel’s excellent book Marking Time: The Epic Quest to Invent the Perfect Calendar (2000) discusses both the charming idiosyncrasy of the Swedish calendar for 1712 and the ambiguity of Washington’s birthday in greater detail. The future implications of redefining Coordinated Universal Time will be discussed at the colloquium “Decoupling Civil Timekeeping from Earth Rotation” in Exton, Pennsylvania, on October 5–6, 2011. Proceedings and information will be published at

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