Friday Fun: Calendar Outtakes

The best part of a comedy film is when the actors make small mistakes, and the cast and crew bust out laughing. It’s become common to run outtakes during the credits (by the way, this was first done by Peter Sellers in Being There, in 1979).

Here, I want to share some odd, silly, and independently interesting factoids about how our calendar systems have come up short—sometimes with dire consequences. These factoids all come from Nachum Dershowitz & Edward Reingold’s Calendrical Calculations, which I used last November for my dual posts on Thanksgiving and Hanukkah.

First up, a manufacturing disaster:

“…a computer software error at the Tiwai Point aluminum smelter at midnight on New Year’s Eve [in 1996] caused more than A$1 million of damage. The software error was the failure to consider 1996 a leap year; the same problem occurred 2 hours later at Comalco’s Bell Bay smelter in Tasmania.” [Reported in New Zealand Herald, 8 January 1997.]

This next one was an inconvenience for business travelers:

“…Microsoft Windows 95, 98, and NT get the start of daylight saving time wrong for years, like 2001, in which April 1 is a Sunday; in such cases, Windows has daylight saving time starting on April 8. An estimated 40 million to 50 million computers are affected, including some in hotels that are used for wake-up calls.” [Reported in New York Times, 12 January 1999.]

These two examples, while significant, had consequences that were relatively short-lived. But would you believe a calendar irregularity caused repeated political crises over the course of several centuries? It’s true, as the Ottoman Sultans would have told you. Some background information first…

The Ottoman Empire used the Islamic calendar, which is a lunar calendar with 12 months of 29 or 30 days. There are 11 leap days added every 30 years, so the average length of the year is 354 11/30 days. Obviously, this means that the Islamic calendar drifts throughout the solar year (about 11 days each year), and so the months don’t have any real connection to the changing seasons. April is always a spring month, but Ramadan can occur in any season.

Back to our story: when it came to finances, the Ottomans used the Islamic calendar for expenditures, but since many of the revenues came from seasonal activity (like farming), they used a solar calendar for tax collection. There are about 32 solar years for every 33 Islamic years, and in the 33rd year—the şiviş year—the government faced a fiscal crisis and ran the risk of failing to pay its employees (most notably the military). The financial crises easily became political crises, which have come to be known as “şiviş year crises”.

Now, in the US, we had a government shutdown where some federal employees went unpaid for 2 weeks, but could you imagine an entire year? Of course not. Any farsighted government would realize that the problem was coming, and action was often taken to adapt head off any revolt—devaluing the currency, deficit spending, spreading out payments for a few years to cover the gap, but these measures didn’t always avoid economic and political turmoil.

To give one example, the şiviş year 1677 (1088 A.H.) was weathered with significant deficit spending, but by 1687 the government was forced to postpone payments to its soldiers, whereupon the army marched to Edirne and deposed the Sultan Mehmed IV. Looking over some of the other şiviş years, it seems that one good way to avoid the crisis was to conquer a foreign country (Mehmed II greatly relieved his financial worries by taking Constantinople). It’s worth mentioning that Mehmed IV may have avoided his eventual downfall if his troops had been able to capture Vienna.

That’s all for now! You can read more about the şiviş year crises here.


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