{"id":51707,"date":"2026-11-01T09:14:35","date_gmt":"2026-11-01T09:14:35","guid":{"rendered":"https:\/\/www.worldclock.com\/tahtiaikalaskuri\/"},"modified":"2026-11-01T09:14:35","modified_gmt":"2026-11-01T09:14:35","slug":"tahtiaikalaskuri","status":"publish","type":"page","link":"https:\/\/www.worldclock.com\/fi\/tahtiaikalaskuri\/","title":{"rendered":"T\u00e4htiaika- ja juliaanisen p\u00e4iv\u00e4n laskuri"},"content":{"rendered":"<div class=\"wc wc-tool-page wc-tool-page--sidereal\"><header class=\"wc-thero\"><div class=\"wc-thero__text\"><nav class=\"wc-crumbs\" aria-label=\"Breadcrumb\"><ol><li><a href=\"https:\/\/www.worldclock.com\/fi\/\">Maailmankello<\/a><\/li><li><a href=\"https:\/\/www.worldclock.com\/fi\/tyokalut\/\">Aikaty\u00f6kalut<\/a><\/li><li><span aria-current=\"page\">T\u00e4htiaika- ja juliaanisen p\u00e4iv\u00e4n laskuri<\/span><\/li><\/ol><\/nav><p class=\"wc-eyebrow\"><span aria-hidden=\"true\">\ud83c\udf0c<\/span> Ilmainen ty\u00f6kalu<\/p><h1 class=\"wc-thero__title\">T\u00e4htiaika- ja juliaanisen p\u00e4iv\u00e4n laskuri<\/h1><p class=\"wc-thero__lead\">Paikallinen t\u00e4htiaika, Greenwichin t\u00e4htiaika, juliaaninen p\u00e4iv\u00e4 ja modifioitu juliaaninen p\u00e4iv\u00e4 reaaliajassa mille tahansa paikalle ja ajalle.<\/p><\/div><\/header><div class=\"wc-tool\"><div class=\"wc-sid\" data-wc-tool=\"sidereal\" data-default=\"{&quot;n&quot;:&quot;Greenwich&quot;,&quot;t&quot;:&quot;Europe\\\/London&quot;,&quot;f&quot;:&quot;gb&quot;,&quot;a&quot;:51.4769,&quot;o&quot;:-0.0005}\"><div class=\"wc-tbar\"><div class=\"wc-field wc-field--grow\"><span>Sijainti<\/span><div class=\"wc-search wc-search--tool\" data-wc-search data-mode=\"add\"><input type=\"search\" placeholder=\"Hae kaupunkia\u2026\" aria-label=\"Hae kaupunkia\u2026\" autocomplete=\"off\"><ul class=\"wc-search__results\" hidden><\/ul><\/div><\/div><label class=\"wc-field\"><span>Pituusaste \u00b0<\/span><input type=\"number\" step=\"0.0001\" min=\"-180\" max=\"180\" data-lng><\/label><button type=\"button\" class=\"wc-btn wc-btn--ghost\" data-geo>\ud83d\udccd K\u00e4yt\u00e4 sijaintiani<\/button><\/div><div class=\"wc-sunc__place\" data-place><\/div><div class=\"wc-sunc__cards\" data-cards><\/div><div class=\"wc-panel\" style=\"margin-top:16px\"><h2>Muunna p\u00e4iv\u00e4m\u00e4\u00e4r\u00e4<\/h2><label class=\"wc-field\"><span>P\u00e4iv\u00e4m\u00e4\u00e4r\u00e4 &amp; aika (UTC)<\/span><input type=\"datetime-local\" step=\"1\" data-dt><\/label><dl class=\"wc-unix__out\" data-out><\/dl><\/div><\/div><\/div><section class=\"wc-section wc-tool-info\"><div class=\"wc-prose\"><h2>Mit\u00e4 t\u00e4htiaika on?<\/h2><p>T\u00e4htiaika mittaa Maan py\u00f6rimist\u00e4 suhteessa kaukaisiin t\u00e4htiin eik\u00e4 aurinkoon. T\u00e4htivuorokausi on noin <strong>23 tuntia 56 minuuttia 4 sekuntia<\/strong> \u2013 l\u00e4hes nelj\u00e4 minuuttia aurinkovuorokautta lyhyempi \u2013 joten t\u00e4hdet nousevat joka y\u00f6 nelj\u00e4 minuuttia aikaisemmin. T\u00e4htitieteilij\u00e4t k\u00e4ytt\u00e4v\u00e4t <strong>paikallista t\u00e4htiaikaa (LST)<\/strong> kaukoputkien suuntaamiseen: t\u00e4hti on korkeimmillaan taivaalla, kun LST on yht\u00e4 suuri kuin sen rektaskensio.<\/p><p><strong>Juliaaninen p\u00e4iv\u00e4<\/strong> on jatkuva p\u00e4iv\u00e4laskuri 1. tammikuuta 4713 eKr. keskip\u00e4iv\u00e4st\u00e4 UTC, ja sit\u00e4 k\u00e4ytet\u00e4\u00e4n t\u00e4htitieteess\u00e4 kalenterimutkien v\u00e4ltt\u00e4miseksi. <strong>Modifioitu juliaaninen p\u00e4iv\u00e4<\/strong> (MJD) on JD \u2212 2 400 000,5 ja alkaa keskiy\u00f6st\u00e4.<\/p><\/div><\/section><section class=\"wc-section wc-faq\"><h2>Usein kysytty\u00e4<\/h2><details><summary>Miten lasken paikallisen t\u00e4htiajan?<\/summary><p>Laske Greenwichin keskit\u00e4htiaika juliaanisesta p\u00e4iv\u00e4st\u00e4 ja lis\u00e4\u00e4 siihen pituusasteesi tunteina (pituusaste \u00f7 15, it\u00e4 positiivinen). Yll\u00e4 oleva laskuri tekee t\u00e4m\u00e4n reaaliajassa mille tahansa sijainnille.<\/p><\/details><\/section><section class=\"wc-section wc-tools-grid\"><div class=\"wc-section__head\"><h2>Lis\u00e4\u00e4 ilmaisia aikaty\u00f6kaluja<\/h2><a href=\"https:\/\/www.worldclock.com\/fi\/tyokalut\/\">Kaikki ty\u00f6kalut \u2192<\/a><\/div><div class=\"wc-toolcards\"><a class=\"wc-toolcard wc-toolcard--sun\" href=\"https:\/\/www.worldclock.com\/fi\/auringonnousu-auringonlasku\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83c\udf05<\/span><span class=\"wc-toolcard__name\">Auringonnousu- ja auringonlaskulaskuri<\/span><span class=\"wc-toolcard__desc\">Auringonnousu, auringonlasku ja kultainen tunti.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--golden\" href=\"https:\/\/www.worldclock.com\/fi\/kultainen-tunti-laskuri\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83d\udcf8<\/span><span class=\"wc-toolcard__name\">Kultaisen tunnin laskuri<\/span><span class=\"wc-toolcard__desc\">Paras valo valokuviin.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--moon\" href=\"https:\/\/www.worldclock.com\/fi\/kuun-vaihe\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83c\udf15<\/span><span class=\"wc-toolcard__name\">Kuun vaihe t\u00e4n\u00e4\u00e4n<\/span><span class=\"wc-toolcard__desc\">T\u00e4m\u00e4n illan kuu ja kuukalenteri.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--fullmoon\" href=\"https:\/\/www.worldclock.com\/fi\/taysikuukalenteri\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83c\udf1d<\/span><span class=\"wc-toolcard__name\">T\u00e4ysikuukalenteri<\/span><span class=\"wc-toolcard__desc\">T\u00e4ysikuiden p\u00e4iv\u00e4m\u00e4\u00e4r\u00e4t ja nimet.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--moonrise\" href=\"https:\/\/www.worldclock.com\/fi\/kuunnousu-kuunlasku\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83c\udf19<\/span><span class=\"wc-toolcard__name\">Kuunnousu- ja kuunlaskuajat<\/span><span class=\"wc-toolcard__desc\">Milloin kuu nousee ja laskee.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--birthmoon\" href=\"https:\/\/www.worldclock.com\/fi\/kuun-vaihe-syntymapaivana\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83c\udf82<\/span><span class=\"wc-toolcard__name\">Kuu syntym\u00e4p\u00e4iv\u00e4n\u00e4si<\/span><span class=\"wc-toolcard__desc\">Kuu min\u00e4 tahansa p\u00e4iv\u00e4n\u00e4.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--astro\" href=\"https:\/\/www.worldclock.com\/fi\/tahtitieteellinen-kalenteri\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83d\udd2d<\/span><span class=\"wc-toolcard__name\">T\u00e4htitieteellinen kalenteri<\/span><span class=\"wc-toolcard__desc\">Pimennykset, meteorit ja taivaan tapahtumat.<\/span><\/a><a class=\"wc-toolcard wc-toolcard--converter\" href=\"https:\/\/www.worldclock.com\/fi\/aikavyohykemuunnin\/\"><span class=\"wc-toolcard__icon\" aria-hidden=\"true\">\ud83d\udd01<\/span><span class=\"wc-toolcard__name\">Aikavy\u00f6hykemuunnin<\/span><span class=\"wc-toolcard__desc\">Muunna aika mink\u00e4 tahansa kaupunkien v\u00e4lill\u00e4.<\/span><\/a><\/div><\/section><\/div>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_kad_blocks_custom_css":"","_kad_blocks_head_custom_js":"","_kad_blocks_body_custom_js":"","_kad_blocks_footer_custom_js":"","_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":"","bs_cache_bypass_cache":0,"bs_cache_related_page":0},"class_list":["post-51707","page","type-page","status-publish","hentry"],"acf":[],"taxonomy_info":[],"featured_image_src_large":false,"author_info":{"display_name":"clocker","author_link":"https:\/\/www.worldclock.com\/fi\/author\/clocker\/"},"comment_info":"","_links":{"self":[{"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/pages\/51707","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/comments?post=51707"}],"version-history":[{"count":0,"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/pages\/51707\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.worldclock.com\/fi\/wp-json\/wp\/v2\/media?parent=51707"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}