<P> An unexpected adverse effect of daylight saving time may lie in the fact that an extra part of morning rush hour traffic occurs before dawn and traffic emissions then cause higher air pollution than during daylight hours . </P> <P> In 2017, researchers at the University of Washington and the University of Virginia reported that judges who experienced sleep deprivation as a result of DST tended to issue longer sentences . </P> <P> DST's clock shifts have the obvious disadvantage of complexity . People must remember to change their clocks; this can be time - consuming, particularly for mechanical clocks that cannot be moved backward safely . People who work across time zone boundaries need to keep track of multiple DST rules, as not all locations observe DST or observe it the same way . The length of the calendar day becomes variable; it is no longer always 24 hours . Disruption to meetings, travel, broadcasts, billing systems, and records management is common, and can be expensive . During an autumn transition from 02: 00 to 01: 00, a clock reads times from 01: 00: 00 through 01: 59: 59 twice, possibly leading to confusion . </P> <P> Damage to a German steel facility occurred during a DST transition in 1993, when a computer timing system linked to a radio time synchronization signal allowed molten steel to cool for one hour less than the required duration, resulting in spattering of molten steel when it was poured . Medical devices may generate adverse events that could harm patients, without being obvious to clinicians responsible for care . These problems are compounded when the DST rules themselves change; software developers must test and perhaps modify many programs, and users must install updates and restart applications . Consumers must update devices such as programmable thermostats with the correct DST rules or manually adjust the devices' clocks . A common strategy to resolve these problems in computer systems is to express time using the Coordinated Universal Time (UTC) rather than the local time zone . For example, Unix - based computer systems use the UTC - based Unix time internally . </P>

When is daylight savings 2018 how does it work