When time jumps ahead, or back

Daylight Saving Time (DST) is a common technique in many of world's large countries which sets clocks forward in summer and backward in winter to change our daily schedule and thus affect consumption of artificial light and energy, and increase consumption of daylight. In United States, for example, clocks are set one hour ahead in summer, so that even with same timetable, people wake up one hour early and thus enjoy longer evenings and early morning light. In winter, difference is eliminated by setting clocks one hour back again. On the day of change, at midnight, suddenly there is 1pm after 11:59:59pm in summer (one hour lost to history) or 0:00:00am after 0:59:59am (one hour recorded twice). This quirk of continuous timeline has resulted in some very funny, and other tragic, incidents. Consider the following...

In September 1999, the West Bank was on Daylight Saving Time while Israel had just switched back to standard time. West Bank terrorists prepared time bombs and smuggled them to their Israeli counterparts, who misunderstood the time on the bombs. As the bombs were being planted, they exploded--one hour too early--killing three terrorists instead of the intended victims--two busloads of people.

[D]uring the 1950s and 1960s when each U.S. locality could start and end Daylight Saving Time as it desired. One year, 23 different pairs of DST start and end dates were used in Iowa alone. For exactly five weeks each year, Boston, New York, and Philadelphia were not on the same time as Washington D.C., Cleveland, or Baltimore--but Chicago was. And, on one Ohio to West Virginia bus route, passengers had to change their watches seven times in 35 miles!

Patrons of bars that stay open past 2:00 a.m. lose one hour of drinking time on the day when Daylight Saving Time springs forward one hour. This has led to annual problems in numerous locations, and sometimes even to riots.

To keep to their published timetables, trains cannot leave a station before the scheduled time. So, when the clocks fall back one hour in October, all Amtrak trains in the U.S. that are running on time stop at 2:00 a.m. and wait one hour before resuming. Overnight passengers are often surprised to find their train at a dead stop and their travel time an hour longer than expected. At the spring Daylight Saving Time change, trains instantaneously become an hour behind schedule at 2:00 a.m., but they just keep going and do their best to make up the time.

All these and more from webexhibits.org.