Ra'ayin Masu Shirye-shiryen Game da Lokacin Unix

na tuba Patrick McKenzie.

Jiya Danny Na yi tambaya game da wasu abubuwa masu ban sha'awa game da lokacin Unix, kuma na tuna cewa wani lokacin yana aiki gaba ɗaya ba tare da fahimta ba.

Waɗannan abubuwa guda uku sun yi kama da ma’ana da ma’ana, ko ba haka ba?

1. Lokacin Unix shine adadin daƙiƙa tun 1 ga Janairu, 1970 00:00:00 UTC.
2. Idan ka jira daidai dakika ɗaya, lokacin Unix zai canza da daƙiƙa ɗaya daidai.
3. Lokacin Unix baya motsawa baya.

Babu ɗayan waɗannan da ke gaskiya.

Amma bai isa kawai a ce, “Ba ɗaya daga cikin waɗannan da ke gaskiya ba,” ba tare da bayyanawa ba. me yasa. Duba ƙasa don bayani. Amma idan kuna son yin tunani da kanku, kar ku gungurawa hoton agogo!

Agogon tebur daga 1770s. John Leroux ne ya tattara. Daga Tarin barka da zuwa. An buga ƙarƙashin lasisi CC BY

Dukkan kuskure guda uku suna da dalili guda: tsalle seconds. Idan ba ku saba da tsalle-tsalle ba, ga saurin tunani:

An ƙayyade lokacin UTC da abubuwa biyu:

• Lokacin Atomic na Duniya: Matsakaicin karatu daga ɗaruruwan agogon atomic a duniya. Za mu iya auna na biyu ta hanyar sifofin lantarki na zarra, kuma wannan shine mafi daidaitaccen ma'aunin lokacin da kimiyya ta sani.
• Zaman Duniya, bisa jujjuyawar da duniya ke yi a kusa da nata axis. Juyi daya cikakke shine rana daya.

Matsalar ita ce waɗannan lambobi biyu ba sa daidaita koyaushe. Jujjuyawar Duniya ba ta daidaita ba - sannu a hankali tana raguwa, don haka kwanakin a cikin Zamanin Duniya suna kara tsayi. A gefe guda, agogon atomic daidaitattun shaidan kuma suna dawwama cikin miliyoyin shekaru.

Lokacin da sau biyu suka daina aiki tare, ana ƙara ko cire na biyu daga UTC don dawo da su cikin aiki tare. Tun 1972 sabis IERS (wanda ke gudanar da wannan harka) ya ƙara ƙarin daƙiƙa 27. Sakamakon ya kasance kwanaki 27 UTC tare da tsawon daƙiƙa 86. A ka'ida, yini mai tsayin daƙiƙa 401 (ban da ɗaya) yana yiwuwa. Duk zaɓuɓɓukan biyu sun saba wa ainihin zato na lokacin Unix.

Lokacin Unix yana ɗauka cewa kowace rana tana ɗaukar daƙiƙa 86 daidai (400 × 60 × 60 = 24), ba tare da ƙarin daƙiƙa ba. Idan irin wannan tsalle ya faru, to, lokacin Unix ya yi tsalle daƙiƙa ɗaya, ko ƙidaya daƙiƙa biyu a ɗaya. Ya zuwa 86, ya ɓace 400 leap seconds.

Don haka muna bukatar a kara mana kura-kurai kamar haka:

• Lokacin Unix shine adadin daƙiƙa tun 1 ga Janairu, 1970 00:00:00 UTC debe tsalle tsalle.
• Idan kun jira daidai dakika ɗaya, lokacin Unix zai canza daidai da daƙiƙa ɗaya, sai dai idan an cire tsalle na biyu.

  Har ya zuwa yanzu, ba a taɓa cire daƙiƙa a aikace ba (kuma jinkirin jujjuyawar duniya yana nufin wannan ba zai yuwu ba), amma idan hakan ya taɓa faruwa, yana nufin cewa ranar UTC zata zama ɗan gajeren daƙiƙa ɗaya. A wannan yanayin, ana jefar da na biyu na ƙarshe na UTC (23:59:59).

  Kowace ranar Unix tana da adadin daƙiƙa guda ɗaya, don haka Unix na ƙarshe na daƙiƙa na ƙarshen rana ba zai dace da kowane lokacin UTC ba. Ga yadda yake kama, a cikin tazarar kwata da biyu:

  
  
  Idan kun fara a 23:59:58:00 UTC kuma ku jira daƙiƙa ɗaya, lokacin Unix zai wuce daƙiƙa biyu na UTC kuma ba za a sanya tambarin Unix 101 ga kowa ba.

• Lokacin Unix ba zai taɓa komawa baya ba, har sai an kara dakika tsalle.

  Wannan ya riga ya faru sau 27 a aikace. A ƙarshen ranar UTC, ana ƙara ƙarin daƙiƙa a 23:59:60. Unix yana da adadin daƙiƙa guda ɗaya a cikin yini, don haka ba zai iya ƙara ƙarin daƙiƙa ba - a maimakon haka sai ta maimaita tambarin Unix na daƙiƙa na ƙarshe. Ga yadda yake kama, a cikin tazarar kwata da biyu:

  
  
  Idan kun fara a 23:59:60.50 kuma ku jira rabin daƙiƙa, lokacin Unix dawo da rabin daƙiƙa, kuma Unix 101 timestamp yayi daidai da daƙiƙa biyu na UTC.

Wataƙila waɗannan ba su ne kawai abubuwan ban mamaki na lokutan Unix ba - kawai abin da na tuna jiya.

Lokaci - sosai bakon abu.

source: www.habr.com