Dating Yourself

By Wayne A. Conaway and Terri Morrison
© Copyright 2004, All Rights Reserved

We have become so accustomed to crossing time zones that it is easy to forget that the very concept of universal, globe-spanning chronology is a recent convention. Before the adoption of time zones and universal time, each town set its own time. Noon was whenever the sun was directly overhead, and clocks were set by it.

The adoption of time zones started with modern transportation. As we entered the industrial age, and trains crossed continents, the differences between local times became obvious. During a short train ride, it was quite possible to arrive earlier than you left – not because you crossed a time zone, but because local times varied by as much as an hour! Efficient train schedules required the adoption of a universally accepted time. In 1883, the railroads created four time zones to span the contiguous United States of America. The following year, representatives from 24 nations met at the Prime Meridian Conference in Washington, DC. Out of this meeting evolved the time systems we use today, including Greenwich Mean Time, the more accurate Universal Coordinated Time (which includes leap seconds), and the Zulu Time used by air traffic controllers. ("Zulu Time" has nothing to do with the inhabitants of southern Africa. The term comes from the International Civil Aviation Organization's phonetic code. As in the US Military Alphabet, "A" is pronounced "Alpha," "B" is "Bravo," "C" is "Charlie"...down to "Z" for "Zulu.")

This establishes the time of day. But what about the day itself? Calendars have long been a point of difference between nations and religions. For secular purposes, most of the world uses the Gregorian calendar, named after Pope Gregory XIII. He approved a revision of the old Julian (Roman) calendar in 1582.

However, the Gregorian reform was not adopted simultaneously in each country. Europe's Protestant states usually waited until much later to change. England (and its American colonies) did not adopt the Gregorian calendar until 1752. And by that point, 11 days had to be deleted to bring the Julian calendar in synch with the Gregorian one. The Julian calendar is still used in the Greek Orthodox church and in Ukraine. Orthodox feast days now generally run 13 days behind the Gregorian calendar.

The Gregorian calendar is a solar calendar, based on a seasonal year of 365.2422 days per year.

But the sun is not the only way to calculate a year. For example, Muslims utilize a lunar based calendar, which is approximately 11 days shorter. Obviously, the two views of the time are not synchronized. In relation to the Gregorian calendar, Muslim holidays generally advance about 10 days each year. The last celebration of Ramadan, (which occurs in the ninth month of the Muslim year), began on November 27th, 2000. The next Ramadan will begin on or about November 17th, 2001. (The date is approximate because months are calculated by sightings of the moon.)

Another different aspect of the Muslim calendar is the workweek. Since Friday is Islam's holiest day of the week, many (but not all!) countries with Muslim majorities start their workweek on Saturday.

The Hebrew calendar was originally a lunar calendar, but adopted some aspects of solar calendars in the 4th Century AD. This system, still in use today, mandates the use of 19-year cycles. The variation between the Hebrew and Gregorian calendars is about a month. Thus, the Jewish New Year (Rosh Hashanah) will generally fall between mid-September and mid-October. The Jewish Festival of Lights (Chanukah) usually occurs in December.

As with the Muslim calendar, the Hebrew calendar changes the workweek. The Jewish Sabbath begins at sundown on Friday and ends at sundown on Saturday. In Israel, where the Hebrew calendar is used, Sunday is the start of the workweek, and most people take Friday and Saturday off.

For better or worse, most of the world (including air traffic controllers) has decided to use the Gregorian calendar for secular purposes. However, there is one adaptation sometimes made to non-Christians. To differentiate between the Christian and pre-Christian eras, the initials AD (for anno Domini: "the year of our Lord") or BC ("before Christ") are traditionally added to the year. In deference to non-Christian sensibilities, the initials CE (Common Era) and BCE (Before Common Era) have been created. This is a small concession to make to a largely non-Christian world which, like it or not, uses a calendar adopted by a Roman Catholic Pope almost 250 years ago.

Excerpted from OAG Frequent Flyer, August 4, 2001