Yaz Saati Uygulaması Programlama

Programlama




2001 yılında ABD'deki insanların saatlerini el ile ayarlamasını hatırlatan bir genel hizmet reklamı


Birçok bilgisayar tabanlı sistem, temel aldığı zaman dilimine göre YSU'nun başlangıcı veya bitişiyle beraber otomatik olarak saatlerini ayarlayabilmektedir Ancak YSU'daki değişiklikler kimi kurulumlarda sorunlara yol açar Örneğin, Kuzey Amerika'da 2007'de yapılan değişiklikler sonrasında birçok bilgisayar sistemi güncellenme gereği duydu Bu da Microsoft Outlook gibi e-posta ve takvim yazılımlarını büyük ölçüde etkiledi Bu da birlik halindeki bilgi teknolojisi uzmanlarının büyük bir emek kaybına uğramasına yol açtı[102] Bazı uygulamalar YSU'ya odaklanarak saat değişikliklerinden ve zaman diliminden kaynaklanan sorunlardan korunmak üzere özelleşmiş durumdadır[103]
Günümüzde bu alanda en yaygın olarak kullanılan bilgisayar tabanlı uygulamalar zoneinfo ve Microsoft Windows'tur
Zoneinfo
The zoneinfo database maps a name to the named location's historical and predicted clock shifts This database is used by many computer software systems, including most Unix-like operating systems, Java, and Oracle;[104] HP's "tztab" database is similar but incompatible[105] When temporal authorities change DST rules, zoneinfo updates are installed as part of ordinary system maintenance In Unix-like systems the TZ environment variable specifies the location name, as in TZ='America/New_York'
Older or stripped-down systems may support only the TZ values required by POSIX, which specify at most one start and end rule explicitly in the value For example, TZ='EST5EDT,M320/02:00,M1110/02:00' specifies time for eastern North America starting in 2007 TZ must be changed whenever DST rules change, and the new TZ value applies to all years, mishandling some older time stamps[106]
Microsoft Windows
As with zoneinfo, a user of Microsoft Windows configures DST by specifying the name of a location, and the operating system then consults a table of rule sets that must be updated when DST rules change Procedures for specifying the name and updating the table vary with release Updates are not issued for older versions of Microsoft Windows[107] Windows Vista supports at most two start and end rules per time zone setting In a Canadian location observing DST, a single Vista setting supports both 1987-2006 and post-2006 time stamps, but mishandles some older time stamps Older Microsoft Windows systems usually store only a single start and end rule for each zone, so that the same Canadian setting reliably supports only post-2006 time stamps[108]
These limitations have caused problems For example, before 2005, DST in Israel varied each year and was skipped some years Windows 95 used rules correct for 1995 only, causing problems in later years In Windows 98 Microsoft gave up and marked Israel as not having DST, forcing Israeli users to shift their computer clocks manually twice a year The 2005 Israeli Daylight Saving Law established predictable rules using the Jewish calendar but Windows zone files cannot represent the rules' dates in a year-independent way Partial workarounds, which mishandle older time stamps, include manually switching zone files every year[109] and a Microsoft tool that switches zones automatically[110]
Microsoft Windows keeps the system real-time clock in local time This causes several problems, including compatibility when multi booting with operating systems that set the clock to UTC, and double-adjusting the clock when multi booting different Windows versions, such as with a rescue boot disk In 2008 Microsoft hinted that future versions of Windows will partially support a Windows registry entry RealTimeIsUniversal that had been introduced many years earlier, when Windows NT supported RISC machines with UTC clocks, but had not been maintained since[111]

Kaynak : Wikipedia