Sunday, Sept. 8 would normally have been the day when Israelis ended daylight saving time, which would have hastened the end of Yom Kippur, the 25-hour fast that lasts from sunset on Friday, Sept. 13, to nightfall on Saturday, Sept. 14.

Yet in July, the Knesset approved a plan to extend daylight saving time to Oct. 27.

The problem is that not everyone got the memo. Many mobile phones in Israel were already programmed to effect the clock change over last weekend and so failed to delay the time change until the new date in October. The snafu affected some Google phones, iPhones, Android and iOS software, BlackBerrys and Symbian phones.

As a result, while many Israelis awoke on time on Sunday, which is a work day in Israel, others slept in as their cell phones erroneously slipped back an hour.

Moshe Berghoff, IT director at Chabad.org who oversees the site`s popular Jewish calendar feature, says he was tipped off early enough to program the appropriate changes.

“Keeping track of DST is a never-ending job,” he says. “It’s a moving target. Countries are constantly changing rules for a host of reasons, including power conservation, and every time they change, we need to update our algorithms to match. Just to add to the mix, you have counties in the Southern Hemisphere—like Chile, which decided to set their clocks forward an hour on Sept. 8—that are moving exactly in the opposite direction as we are in the Northern Hemisphere.”

Since people use Chabad.org to calculate Jewish birth dates and yahrtzeits (anniversaries of passing) reaching all the way back to the 1800s, and Jewish dates begin at nightfall, which varies from day to day, Berghoff says “we’ve had the additional challenge of maintaining historical records of when daylight saving time began and ended every year in many locations around the globe, all the way back to when they began nearly a century ago. This allows people to enter the moment of death or birth, and us to accurately tell when nightfall was on that particular date at that particular time.”

In spite of the challenges, Berghoff reports, “through carefully monitoring everything—with the help of some astute users—we generally stay on top of our game.”