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mw-ui-icon-wikimedia-userAdd"></span> <span>アカウント作成</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=%E7%89%B9%E5%88%A5:%E3%83%AD%E3%82%B0%E3%82%A4%E3%83%B3&returnto=%E5%85%83%E6%9C%9F" title="ログインすることを推奨します。ただし、必須ではありません。 [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>ログイン</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> ログアウトした編集者のページ <a href="/wiki/Wikipedia:%E3%82%A6%E3%82%A3%E3%82%AD%E3%83%9A%E3%83%87%E3%82%A3%E3%82%A2%E3%81%B8%E3%82%88%E3%81%86%E3%81%93%E3%81%9D" aria-label="編集の詳細"><span>もっと詳しく</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/%E7%89%B9%E5%88%A5:%E8%87%AA%E5%88%86%E3%81%AE%E6%8A%95%E7%A8%BF%E8%A8%98%E9%8C%B2" title="このIPアドレスからなされた編集の一覧 [y]" accesskey="y"><span>投稿記録</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/%E7%89%B9%E5%88%A5:%E3%83%88%E3%83%BC%E3%82%AF%E3%83%9A%E3%83%BC%E3%82%B8" title="このIPアドレスからなされた編集についての議論 [n]" accesskey="n"><span>トーク</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="サイト"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="目次" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">目次</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">サイドバーに移動</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">非表示</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">ページ先頭</div> </a> </li> <li id="toc-天体観測における元期" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#天体観測における元期"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>天体観測における元期</span> </div> </a> <ul id="toc-天体観測における元期-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-測量における元期" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#測量における元期"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>測量における元期</span> </div> </a> <ul id="toc-測量における元期-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-コンピュータにおける元期" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#コンピュータにおける元期"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>コンピュータにおける元期</span> </div> </a> <button aria-controls="toc-コンピュータにおける元期-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>コンピュータにおける元期サブセクションを切り替えます</span> </button> <ul id="toc-コンピュータにおける元期-sublist" class="vector-toc-list"> <li id="toc-Unixにおける元期" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Unixにおける元期"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Unixにおける元期</span> </div> </a> <ul id="toc-Unixにおける元期-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Classic_Mac_OSにおける元期" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Classic_Mac_OSにおける元期"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Classic Mac OSにおける元期</span> </div> </a> <ul id="toc-Classic_Mac_OSにおける元期-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-脚注" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#脚注"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>脚注</span> </div> </a> <button aria-controls="toc-脚注-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>脚注サブセクションを切り替えます</span> </button> <ul id="toc-脚注-sublist" class="vector-toc-list"> <li id="toc-注釈" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#注釈"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>注釈</span> </div> </a> <ul id="toc-注釈-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-出典" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#出典"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>出典</span> </div> </a> <ul id="toc-出典-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-関連項目" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#関連項目"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>関連項目</span> </div> </a> <ul id="toc-関連項目-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="目次" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="目次" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="目次の表示・非表示を切り替え" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">目次の表示・非表示を切り替え</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">元期</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="特定の記事の別の言語版に移動します。利用可能な言語55件" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-55" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">55の言語版</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Epog_(sterrekunde)" title="アフリカーンス語: Epog (sterrekunde)" lang="af" hreflang="af" data-title="Epog (sterrekunde)" data-language-autonym="Afrikaans" data-language-local-name="アフリカーンス語" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D8%AD%D9%82%D8%A8%D8%A9_(%D8%B9%D9%84%D9%85_%D8%A7%D9%84%D9%81%D9%84%D9%83)" title="アラビア語: حقبة (علم الفلك)" lang="ar" hreflang="ar" data-title="حقبة (علم الفلك)" data-language-autonym="العربية" data-language-local-name="アラビア語" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/D%C3%B3mina_(astronom%C3%ADa)" title="アストゥリアス語: Dómina (astronomía)" lang="ast" hreflang="ast" data-title="Dómina (astronomía)" data-language-autonym="Asturianu" data-language-local-name="アストゥリアス語" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%AD%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%B0%D0%BD%D0%BE%D0%BC%D1%96%D1%8F)" title="ベラルーシ語: Эпоха (астраномія)" lang="be" hreflang="be" data-title="Эпоха (астраномія)" data-language-autonym="Беларуская" data-language-local-name="ベラルーシ語" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/%D0%AD%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%B0%D0%BD%D0%BE%D0%BC%D1%96%D1%8F)" title="Belarusian (Taraškievica orthography): Эпоха (астраномія)" lang="be-tarask" hreflang="be-tarask" data-title="Эпоха (астраномія)" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%95%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%8F)" title="ブルガリア語: Епоха (астрономия)" lang="bg" hreflang="bg" data-title="Епоха (астрономия)" data-language-autonym="Български" data-language-local-name="ブルガリア語" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AA%E0%A7%8D%E0%A6%B0%E0%A6%B8%E0%A6%99%E0%A7%8D%E0%A6%97%E0%A6%A4%E0%A6%BF%E0%A6%A5%E0%A6%BF_(%E0%A6%9C%E0%A7%8D%E0%A6%AF%E0%A7%8B%E0%A6%A4%E0%A6%BF%E0%A6%B0%E0%A7%8D%E0%A6%AC%E0%A6%BF%E0%A6%9C%E0%A7%8D%E0%A6%9E%E0%A6%BE%E0%A6%A8)" title="ベンガル語: প্রসঙ্গতিথি (জ্যোতির্বিজ্ঞান)" lang="bn" hreflang="bn" data-title="প্রসঙ্গতিথি (জ্যোতির্বিজ্ঞান)" data-language-autonym="বাংলা" data-language-local-name="ベンガル語" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Epoha_(astronomija)" title="ボスニア語: Epoha (astronomija)" lang="bs" hreflang="bs" data-title="Epoha (astronomija)" data-language-autonym="Bosanski" data-language-local-name="ボスニア語" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/%C3%88poca_(astronomia)" title="カタロニア語: Època (astronomia)" lang="ca" hreflang="ca" data-title="Època (astronomia)" data-language-autonym="Català" data-language-local-name="カタロニア語" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Ekvinokcium" title="チェコ語: Ekvinokcium" lang="cs" hreflang="cs" data-title="Ekvinokcium" data-language-autonym="Čeština" data-language-local-name="チェコ語" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Epoche_(Astronomie)" title="ドイツ語: Epoche (Astronomie)" lang="de" hreflang="de" data-title="Epoche (Astronomie)" data-language-autonym="Deutsch" data-language-local-name="ドイツ語" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%95%CF%80%CE%BF%CF%87%CE%AE_(%CE%B1%CF%83%CF%84%CF%81%CE%BF%CE%BD%CE%BF%CE%BC%CE%AF%CE%B1)" title="ギリシャ語: Εποχή (αστρονομία)" lang="el" hreflang="el" data-title="Εποχή (αστρονομία)" data-language-autonym="Ελληνικά" data-language-local-name="ギリシャ語" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-en mw-list-item"><a href="https://en.wikipedia.org/wiki/Epoch_(astronomy)" title="英語: Epoch (astronomy)" lang="en" hreflang="en" data-title="Epoch (astronomy)" data-language-autonym="English" data-language-local-name="英語" class="interlanguage-link-target"><span>English</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Epoko_(astronomio)" title="エスペラント語: Epoko (astronomio)" lang="eo" hreflang="eo" data-title="Epoko (astronomio)" data-language-autonym="Esperanto" data-language-local-name="エスペラント語" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/%C3%89poca_(astronom%C3%ADa)" title="スペイン語: Época (astronomía)" lang="es" hreflang="es" data-title="Época (astronomía)" data-language-autonym="Español" data-language-local-name="スペイン語" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Garai_(astronomia)" title="バスク語: Garai (astronomia)" lang="eu" hreflang="eu" data-title="Garai (astronomia)" data-language-autonym="Euskara" data-language-local-name="バスク語" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%D8%A8%D8%AF%D8%A3_(%D8%A7%D8%AE%D8%AA%D8%B1%D8%B4%D9%86%D8%A7%D8%B3%DB%8C)" title="ペルシア語: مبدأ (اخترشناسی)" lang="fa" hreflang="fa" data-title="مبدأ (اخترشناسی)" data-language-autonym="فارسی" data-language-local-name="ペルシア語" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Epookki_(t%C3%A4htitiede)" title="フィンランド語: Epookki (tähtitiede)" lang="fi" hreflang="fi" data-title="Epookki (tähtitiede)" data-language-autonym="Suomi" data-language-local-name="フィンランド語" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/%C3%89poque_(astronomie)" title="フランス語: Époque (astronomie)" lang="fr" hreflang="fr" data-title="Époque (astronomie)" data-language-autonym="Français" data-language-local-name="フランス語" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/%C3%89poca_(astronom%C3%ADa)" title="ガリシア語: Época (astronomía)" lang="gl" hreflang="gl" data-title="Época (astronomía)" data-language-autonym="Galego" data-language-local-name="ガリシア語" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%AA%D7%A7%D7%95%D7%A4%D7%AA_%D7%99%D7%99%D7%97%D7%95%D7%A1_(%D7%90%D7%A1%D7%98%D7%A8%D7%95%D7%A0%D7%95%D7%9E%D7%99%D7%94)" title="ヘブライ語: תקופת ייחוס (אסטרונומיה)" lang="he" hreflang="he" data-title="תקופת ייחוס (אסטרונומיה)" data-language-autonym="עברית" data-language-local-name="ヘブライ語" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AF%E0%A5%81%E0%A4%97%E0%A4%BE%E0%A4%B0%E0%A4%AE%E0%A5%8D%E0%A4%AD_(%E0%A4%96%E0%A4%97%E0%A5%8B%E0%A4%B2%E0%A4%B6%E0%A4%BE%E0%A4%B8%E0%A5%8D%E0%A4%A4%E0%A5%8D%E0%A4%B0)" title="ヒンディー語: युगारम्भ (खगोलशास्त्र)" lang="hi" hreflang="hi" data-title="युगारम्भ (खगोलशास्त्र)" data-language-autonym="हिन्दी" data-language-local-name="ヒンディー語" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Epoha_(astronomija)" title="クロアチア語: Epoha (astronomija)" lang="hr" hreflang="hr" data-title="Epoha (astronomija)" data-language-autonym="Hrvatski" data-language-local-name="クロアチア語" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%B7%D5%BA%D5%B8%D5%AD%D5%A1_(%D5%A1%D5%BD%D5%BF%D5%B2%D5%A1%D5%A3%D5%AB%D5%BF%D5%B8%D6%82%D5%A9%D5%B5%D5%B8%D6%82%D5%B6)" title="アルメニア語: Էպոխա (աստղագիտություն)" lang="hy" hreflang="hy" data-title="Էպոխա (աստղագիտություն)" data-language-autonym="Հայերեն" data-language-local-name="アルメニア語" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Epos_(astronomi)" title="インドネシア語: Epos (astronomi)" lang="id" hreflang="id" data-title="Epos (astronomi)" data-language-autonym="Bahasa Indonesia" data-language-local-name="インドネシア語" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Epoca_(astronomia)" title="イタリア語: Epoca (astronomia)" lang="it" hreflang="it" data-title="Epoca (astronomia)" data-language-autonym="Italiano" data-language-local-name="イタリア語" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%94%E1%83%9E%E1%83%9D%E1%83%A5%E1%83%90_(%E1%83%90%E1%83%A1%E1%83%A2%E1%83%A0%E1%83%9D%E1%83%9C%E1%83%9D%E1%83%9B%E1%83%98%E1%83%90)" title="ジョージア語: ეპოქა (ასტრონომია)" lang="ka" hreflang="ka" data-title="ეპოქა (ასტრონომია)" data-language-autonym="ქართული" data-language-local-name="ジョージア語" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%97%AD%EA%B8%B0%EC%A0%90" title="韓国語: 역기점" lang="ko" hreflang="ko" data-title="역기점" data-language-autonym="한국어" data-language-local-name="韓国語" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Epocha_(astronomia)" title="ラテン語: Epocha (astronomia)" lang="la" hreflang="la" data-title="Epocha (astronomia)" data-language-autonym="Latina" data-language-local-name="ラテン語" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lb mw-list-item"><a href="https://lb.wikipedia.org/wiki/Epoch_(Astronomie)" title="ルクセンブルク語: Epoch (Astronomie)" lang="lb" hreflang="lb" data-title="Epoch (Astronomie)" data-language-autonym="Lëtzebuergesch" data-language-local-name="ルクセンブルク語" class="interlanguage-link-target"><span>Lëtzebuergesch</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Epocha_(astronomija)" title="リトアニア語: Epocha (astronomija)" lang="lt" hreflang="lt" data-title="Epocha (astronomija)" data-language-autonym="Lietuvių" data-language-local-name="リトアニア語" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%95%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%98%D0%B0)" title="マケドニア語: Епоха (астрономија)" lang="mk" hreflang="mk" data-title="Епоха (астрономија)" data-language-autonym="Македонски" data-language-local-name="マケドニア語" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%AF%E0%A5%81%E0%A4%97_(%E0%A4%96%E0%A4%97%E0%A5%8B%E0%A4%B2%E0%A4%B6%E0%A4%BE%E0%A4%B8%E0%A5%8D%E0%A4%A4%E0%A5%8D%E0%A4%B0)" title="マラーティー語: युग (खगोलशास्त्र)" lang="mr" hreflang="mr" data-title="युग (खगोलशास्त्र)" data-language-autonym="मराठी" data-language-local-name="マラーティー語" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Epok_(astronomi)" title="マレー語: Epok (astronomi)" lang="ms" hreflang="ms" data-title="Epok (astronomi)" data-language-autonym="Bahasa Melayu" data-language-local-name="マレー語" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Epoche_(astronomie)" title="オランダ語: Epoche (astronomie)" lang="nl" hreflang="nl" data-title="Epoche (astronomie)" data-language-autonym="Nederlands" data-language-local-name="オランダ語" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Astronomisk_epoke" title="ノルウェー語(ニーノシュク): Astronomisk epoke" lang="nn" hreflang="nn" data-title="Astronomisk epoke" data-language-autonym="Norsk nynorsk" data-language-local-name="ノルウェー語(ニーノシュク)" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Epoke_(astronomi)" title="ノルウェー語(ブークモール): Epoke (astronomi)" lang="nb" hreflang="nb" data-title="Epoke (astronomi)" data-language-autonym="Norsk bokmål" data-language-local-name="ノルウェー語(ブークモール)" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Epoka_(astronomia)" title="ポーランド語: Epoka (astronomia)" lang="pl" hreflang="pl" data-title="Epoka (astronomia)" data-language-autonym="Polski" data-language-local-name="ポーランド語" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/%C3%89poca_(astronomia)" title="ポルトガル語: Época (astronomia)" lang="pt" hreflang="pt" data-title="Época (astronomia)" data-language-autonym="Português" data-language-local-name="ポルトガル語" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Epoc%C4%83_(astronomie)" title="ルーマニア語: Epocă (astronomie)" lang="ro" hreflang="ro" data-title="Epocă (astronomie)" data-language-autonym="Română" data-language-local-name="ルーマニア語" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%AD%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%8F)" title="ロシア語: Эпоха (астрономия)" lang="ru" hreflang="ru" data-title="Эпоха (астрономия)" data-language-autonym="Русский" data-language-local-name="ロシア語" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Epoha_(astronomija)" title="セルボ・クロアチア語: Epoha (astronomija)" lang="sh" hreflang="sh" data-title="Epoha (astronomija)" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="セルボ・クロアチア語" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Epoch_(astronomy)" title="シンプル英語: Epoch (astronomy)" lang="en-simple" hreflang="en-simple" data-title="Epoch (astronomy)" data-language-autonym="Simple English" data-language-local-name="シンプル英語" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Epocha_(astron%C3%B3mia)" title="スロバキア語: Epocha (astronómia)" lang="sk" hreflang="sk" data-title="Epocha (astronómia)" data-language-autonym="Slovenčina" data-language-local-name="スロバキア語" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Epoha_(astronomija)" title="スロベニア語: Epoha (astronomija)" lang="sl" hreflang="sl" data-title="Epoha (astronomija)" data-language-autonym="Slovenščina" data-language-local-name="スロベニア語" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%95%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%98%D0%B0)" title="セルビア語: Епоха (астрономија)" lang="sr" hreflang="sr" data-title="Епоха (астрономија)" data-language-autonym="Српски / srpski" data-language-local-name="セルビア語" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Epok_(astronomi)" title="スウェーデン語: Epok (astronomi)" lang="sv" hreflang="sv" data-title="Epok (astronomi)" data-language-autonym="Svenska" data-language-local-name="スウェーデン語" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-szl mw-list-item"><a href="https://szl.wikipedia.org/wiki/Epoka_(astr%C5%8Dn%C5%8Dmij%C5%8F)" title="シレジア語: Epoka (astrōnōmijŏ)" lang="szl" hreflang="szl" data-title="Epoka (astrōnōmijŏ)" data-language-autonym="Ślůnski" data-language-local-name="シレジア語" class="interlanguage-link-target"><span>Ślůnski</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%95%E0%B9%89%E0%B8%99%E0%B8%A2%E0%B8%B8%E0%B8%84%E0%B8%AD%E0%B9%89%E0%B8%B2%E0%B8%87%E0%B8%AD%E0%B8%B4%E0%B8%87_(%E0%B8%94%E0%B8%B2%E0%B8%A3%E0%B8%B2%E0%B8%A8%E0%B8%B2%E0%B8%AA%E0%B8%95%E0%B8%A3%E0%B9%8C)" title="タイ語: ต้นยุคอ้างอิง (ดาราศาสตร์)" lang="th" hreflang="th" data-title="ต้นยุคอ้างอิง (ดาราศาสตร์)" data-language-autonym="ไทย" data-language-local-name="タイ語" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Devir_(astronomi)" title="トルコ語: Devir (astronomi)" lang="tr" hreflang="tr" data-title="Devir (astronomi)" data-language-autonym="Türkçe" data-language-local-name="トルコ語" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%95%D0%BF%D0%BE%D1%85%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D1%96%D1%8F)" title="ウクライナ語: Епоха (астрономія)" lang="uk" hreflang="uk" data-title="Епоха (астрономія)" data-language-autonym="Українська" data-language-local-name="ウクライナ語" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-uz mw-list-item"><a href="https://uz.wikipedia.org/wiki/Davr_(astronomiya)" title="ウズベク語: Davr (astronomiya)" lang="uz" hreflang="uz" data-title="Davr (astronomiya)" data-language-autonym="Oʻzbekcha / ўзбекча" data-language-local-name="ウズベク語" class="interlanguage-link-target"><span>Oʻzbekcha / ўзбекча</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/K%E1%BB%B7_nguy%C3%AAn_(thi%C3%AAn_v%C4%83n_h%E1%BB%8Dc)" title="ベトナム語: Kỷ nguyên (thiên văn học)" lang="vi" hreflang="vi" data-title="Kỷ nguyên (thiên văn học)" data-language-autonym="Tiếng Việt" data-language-local-name="ベトナム語" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E6%9B%86%E5%85%83" title="中国語: 曆元" lang="zh" hreflang="zh" data-title="曆元" data-language-autonym="中文" data-language-local-name="中国語" class="interlanguage-link-target"><span>中文</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E6%9B%86%E5%85%83" title="広東語: 曆元" lang="yue" hreflang="yue" data-title="曆元" data-language-autonym="粵語" data-language-local-name="広東語" class="interlanguage-link-target"><span>粵語</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2703#sitelinks-wikipedia" title="言語間リンクを編集" class="wbc-editpage">リンクを編集</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="名前空間"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/%E5%85%83%E6%9C%9F" title="本文を閲覧 [c]" accesskey="c"><span>ページ</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/%E3%83%8E%E3%83%BC%E3%83%88:%E5%85%83%E6%9C%9F" rel="discussion" title="本文ページについての議論 [t]" accesskey="t"><span>ノート</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="別の言語に切り替える" > <label 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href="/w/index.php?title=%E7%89%B9%E5%88%A5:%E3%83%96%E3%83%83%E3%82%AF&bookcmd=book_creator&referer=%E5%85%83%E6%9C%9F"><span>ブックの新規作成</span></a></li><li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=%E7%89%B9%E5%88%A5:DownloadAsPdf&page=%E5%85%83%E6%9C%9F&action=show-download-screen"><span>PDF 形式でダウンロード</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&printable=yes" title="このページの印刷用ページ [p]" accesskey="p"><span>印刷用バージョン</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> 他のプロジェクト </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q2703" title="関連付けられたデータリポジトリ項目へのリンク [g]" accesskey="g"><span>ウィキデータ項目</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="ページツール"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="表示"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">表示</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">サイドバーに移動</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">非表示</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">出典: フリー百科事典『ウィキペディア（Wikipedia）』</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="ja" dir="ltr"><p><b>元期</b>（げんき、<a href="/wiki/%E8%8B%B1%E8%AA%9E" title="英語">英語</a>: <span lang="en">epoch</span>）とは、時間的な起点をいう語であり、主として<a href="/wiki/%E5%A4%A9%E4%BD%93%E8%A6%B3%E6%B8%AC" title="天体観測">天体観測</a>や<a href="/wiki/%E6%B8%AC%E9%87%8F" title="測量">測量</a>において用いられる。「元期2000.0」といった場合は、西暦2000年1月1日の世界時0時を年数、日数、時間の起点として用いるということである。例えば、<a href="/wiki/%E6%9A%A6%E8%A1%A8%E6%99%82" title="暦表時">暦表時</a>の定義では、T（<a href="/wiki/%E3%83%A6%E3%83%AA%E3%82%A6%E3%82%B9%E5%B9%B4#ユリウス世紀" title="ユリウス年">ユリウス世紀</a>）の起点を1900年<a href="/wiki/1%E6%9C%880%E6%97%A5" title="1月0日">1月0日</a>12時としている。この1900年1月0日12時が、<a href="/wiki/%E6%9A%A6%E8%A1%A8%E6%99%82" title="暦表時">暦表時</a>の元期である。また、<a href="/wiki/%E3%83%A6%E3%83%AA%E3%82%A6%E3%82%B9%E6%97%A5" class="mw-redirect" title="ユリウス日">ユリウス日</a>の元期は、ユリウス暦紀元前4713年1月1日の正午（世界時）である。 </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="天体観測における元期"><span id=".E5.A4.A9.E4.BD.93.E8.A6.B3.E6.B8.AC.E3.81.AB.E3.81.8A.E3.81.91.E3.82.8B.E5.85.83.E6.9C.9F"></span>天体観測における元期</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=1" title="節を編集: 天体観測における元期"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>主に、<a href="/wiki/%E5%BD%97%E6%98%9F" title="彗星">彗星</a>や<a href="/wiki/%E5%B0%8F%E6%83%91%E6%98%9F" title="小惑星">小惑星</a>、<a href="/wiki/%E8%A1%9B%E6%98%9F" title="衛星">衛星</a>などの<a href="/wiki/%E6%83%91%E6%98%9F%E8%BB%8C%E9%81%93" class="mw-redirect" title="惑星軌道">軌道</a>計算の起点を示すのに用いられる。軌道要素がいつ観測されて得たものかを示し、通常は、<a href="/wiki/%E8%A5%BF%E6%9A%A6" title="西暦">西暦</a>とその年の<a href="/wiki/1%E6%9C%881%E6%97%A5" title="1月1日">1月1日</a>から何日過ぎたかで表される（例：<a href="/wiki/2006%E5%B9%B4" title="2006年">2006年</a><a href="/wiki/1%E6%9C%881%E6%97%A5" title="1月1日">1月1日</a><a href="/wiki/%E4%B8%96%E7%95%8C%E6%99%82" title="世界時">UT</a>）。 </p><p>特に、彗星や小惑星など他の惑星などの<a href="/wiki/%E5%BC%95%E5%8A%9B" class="mw-redirect" title="引力">引力</a>の影響を受け、軌道が変化しやすい天体の観測に用いられることが多い。特に、彗星観測などでは、観測ごとに軌道が変化するため、長期的な軌道を算出することが困難である。このため、元期が最新のものを使用することにより、より観測時に正確に近い軌道を知ることができる。 </p><p>歴史的には、元期は、1900年、1950年、2000年（J2000.0）のそれぞれ1月1日の12時（<a href="/wiki/%E6%AD%A3%E5%8D%88" title="正午">正午</a>）が用いられることが多い。 </p> <div class="mw-heading mw-heading2"><h2 id="測量における元期"><span id=".E6.B8.AC.E9.87.8F.E3.81.AB.E3.81.8A.E3.81.91.E3.82.8B.E5.85.83.E6.9C.9F"></span>測量における元期</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=2" title="節を編集: 測量における元期"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/%E5%9C%B0%E6%AE%BB%E5%A4%89%E5%8B%95" title="地殻変動">地殻変動</a>による位置<a href="/wiki/%E5%BA%A7%E6%A8%99" title="座標">座標</a>の歪みを修正するために導入された<a href="/w/index.php?title=%E3%82%BB%E3%83%9F%E3%83%BB%E3%83%80%E3%82%A4%E3%83%8A%E3%83%9F%E3%83%83%E3%82%AF%E8%A3%9C%E6%AD%A3&action=edit&redlink=1" class="new" title="セミ・ダイナミック補正 (存在しないページ)">セミ・ダイナミック補正</a>では、<a href="/w/index.php?title=%E6%B8%AC%E9%87%8F%E6%88%90%E6%9E%9C&action=edit&redlink=1" class="new" title="測量成果 (存在しないページ)">測量成果</a>の基準日を元期という。元期に対して観測を行った時点を今期（こんき）と呼ぶ<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>。 </p><p>2023年現在で公開されている日本の「測量成果2011」における元期は、おおむね東日本では2011年5月24日、西日本では1997年1月1日である。 </p> <div class="mw-heading mw-heading2"><h2 id="コンピュータにおける元期"><span id=".E3.82.B3.E3.83.B3.E3.83.94.E3.83.A5.E3.83.BC.E3.82.BF.E3.81.AB.E3.81.8A.E3.81.91.E3.82.8B.E5.85.83.E6.9C.9F"></span>コンピュータにおける元期</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=3" title="節を編集: コンピュータにおける元期"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="rellink" style="margin-bottom: 0.5em; padding-left: 2em; font-size: 90%;" role="note">→詳細は「<span title="リンク先の項目はまだありません。新規の執筆や他言語版からの翻訳が望まれます。"><a href="/w/index.php?title=%E5%85%83%E6%9C%9F_(%E3%82%B3%E3%83%B3%E3%83%94%E3%83%A5%E3%83%BC%E3%82%BF)&action=edit&redlink=1" class="new" title="元期 (コンピュータ) (存在しないページ)">元期 (コンピュータ)</a><span style="font-size: 0.77em; font-weight: normal;" class="noprint">（<a href="https://en.wikipedia.org/wiki/Epoch_(computing)" class="extiw" title="en:Epoch (computing)">英語版</a>）</span></span>」を参照</div> <div class="mw-heading mw-heading3"><h3 id="Unixにおける元期"><span id="Unix.E3.81.AB.E3.81.8A.E3.81.91.E3.82.8B.E5.85.83.E6.9C.9F"></span>Unixにおける元期</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=4" title="節を編集: Unixにおける元期"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Unix" class="mw-redirect" title="Unix">Unix</a>では<a href="/wiki/%E5%8D%94%E5%AE%9A%E4%B8%96%E7%95%8C%E6%99%82" title="協定世界時">協定世界時</a>1970年1月1日の0時0分0秒が元期と定められている<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>。<a href="/wiki/UNIX%E6%99%82%E9%96%93" title="UNIX時間">UNIX時間</a>はこの元期からの秒数である。 </p> <div class="mw-heading mw-heading3"><h3 id="Classic_Mac_OSにおける元期"><span id="Classic_Mac_OS.E3.81.AB.E3.81.8A.E3.81.91.E3.82.8B.E5.85.83.E6.9C.9F"></span>Classic Mac OSにおける元期</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=5" title="節を編集: Classic Mac OSにおける元期"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Classic_Mac_OS" title="Classic Mac OS">Classic Mac OS</a>（および<span title="リンク先の項目はまだありません。新規の執筆や他言語版からの翻訳が望まれます。"><a href="/w/index.php?title=Macintosh_File_System&action=edit&redlink=1" class="new" title="Macintosh File System (存在しないページ)">Macintosh File System</a><span style="font-size: 0.77em; font-weight: normal;" class="noprint">（<a href="https://en.wikipedia.org/wiki/Macintosh_File_System" class="extiw" title="en:Macintosh File System">英語版</a>）</span></span>、<a href="/wiki/Hierarchical_File_System" title="Hierarchical File System">HFS</a>、<a href="/wiki/HFS_Plus" title="HFS Plus">HFS+</a>）では<a href="/wiki/%E5%8D%94%E5%AE%9A%E4%B8%96%E7%95%8C%E6%99%82" title="協定世界時">協定世界時</a><a href="/wiki/1904%E5%B9%B4" title="1904年">1904年</a><a href="/wiki/1%E6%9C%881%E6%97%A5" title="1月1日">1月1日</a>の0時0分0秒が元期と定められている<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>注釈 1<span class="cite-bracket">]</span></a></sup>。 </p> <div class="mw-heading mw-heading2"><h2 id="脚注"><span id=".E8.84.9A.E6.B3.A8"></span>脚注</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=6" title="節を編集: 脚注"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="noprint" style="float:right; font-size:90%;">[<a href="/wiki/Help:%E8%84%9A%E6%B3%A8/%E8%AA%AD%E8%80%85%E5%90%91%E3%81%91" title="Help:脚注/読者向け"><span title="この欄の操作法">脚注の使い方</span></a>]</div> <div class="mw-heading mw-heading3"><h3 id="注釈"><span id=".E6.B3.A8.E9.87.88"></span>注釈</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=7" title="節を編集: 注釈"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="reflist" style="list-style-type: decimal;"> <ol class="references"> <li id="cite_note-3"><b><a href="#cite_ref-3">^</a></b> <span class="reference-text"><a href="/wiki/1900%E5%B9%B4" title="1900年">1900年</a>ではなく<a href="/wiki/1904%E5%B9%B4" title="1904年">1904年</a>から始めることで、（<a href="/wiki/%E3%82%B0%E3%83%AC%E3%82%B4%E3%83%AA%E3%82%AA%E6%9A%A6" title="グレゴリオ暦">グレゴリオ暦</a>で）<a href="/wiki/1900%E5%B9%B4" title="1900年">1900年</a>が<a href="/wiki/%E5%B9%B3%E5%B9%B4" title="平年">平年</a>なのを回避し、<a href="/wiki/2099%E5%B9%B4" class="mw-redirect" title="2099年">2099年</a>までの<a href="/wiki/%E9%96%8F%E5%B9%B4" title="閏年">閏年</a>判定を（<a href="/wiki/%E3%83%A6%E3%83%AA%E3%82%A6%E3%82%B9%E6%9A%A6" title="ユリウス暦">ユリウス暦</a>と同様に）<a href="/wiki/%E8%A5%BF%E6%9A%A6" title="西暦">西暦</a>年が4で割り切れるか否かに簡略化している。なお、元期からの経過秒数を32ビット整数で保持している関係で、<a href="/wiki/2040%E5%B9%B4" title="2040年">2040年</a><a href="/wiki/2%E6%9C%886%E6%97%A5" title="2月6日">2月6日</a>までしか表現できない。</span> </li> </ol></div> <div class="mw-heading mw-heading3"><h3 id="出典"><span id=".E5.87.BA.E5.85.B8"></span>出典</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=8" title="節を編集: 出典"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <div class="reflist" style="list-style-type: decimal;"> <ol class="references"> <li id="cite_note-1"><b><a href="#cite_ref-1">^</a></b> <span class="reference-text"><a rel="nofollow" class="external autonumber" href="https://www.gsi.go.jp/sokuchikijun/semidyna01.html">[1]</a> セミ・ダイナミック補正国土地理院</span> </li> <li id="cite_note-2"><b><a href="#cite_ref-2">^</a></b> <span class="reference-text"><cite class="citation web" style="font-style:normal">“<a rel="nofollow" class="external text" href="https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_150">Definitions</a>”.  <a href="/wiki/IEEE" title="IEEE">IEEE</a>及び<a href="/wiki/The_Open_Group" title="The Open Group">The Open Group</a> (2018年). <span title="">2020年7月12日</span>閲覧。</cite></span> </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="関連項目"><span id=".E9.96.A2.E9.80.A3.E9.A0.85.E7.9B.AE"></span>関連項目</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=%E5%85%83%E6%9C%9F&action=edit&section=9" title="節を編集: 関連項目"><span>編集</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/%E5%9B%BD%E5%AE%B6%E5%BA%A7%E6%A8%99" title="国家座標">国家座標</a></li></ul> <style data-mw-deduplicate="TemplateStyles:r96783592">.mw-parser-output .asbox{position:relative;overflow:hidden}.mw-parser-output .asbox table{background:transparent}.mw-parser-output .asbox p{margin:0}.mw-parser-output .asbox p+p{margin-top:0.25em}.mw-parser-output .asbox{font-size:90%}.mw-parser-output .asbox-note{font-size:90%}.mw-parser-output .asbox .navbar{position:absolute;top:-0.90em;right:1em;display:none}</style><div role="note" class="metadata plainlinks asbox stub"><table role="presentation"><tbody><tr class="noresize"><td><span typeof="mw:File"><a href="/wiki/%E3%83%95%E3%82%A1%E3%82%A4%E3%83%AB:Saturn_template.svg" class="mw-file-description"><img alt="スタブアイコン" src="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Saturn_template.svg/48px-Saturn_template.svg.png" decoding="async" width="48" height="48" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/d/df/Saturn_template.svg/72px-Saturn_template.svg.png 1.5x, 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