<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> <P> Some clock - shift problems could be avoided by adjusting clocks continuously or at least more gradually--for example, Willett at first suggested weekly 20 - minute transitions--but this would add complexity and has never been implemented . </P>

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