{
    "mode": "perldoc",
    "parameter": "Time::JulianDay",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/perldoc/Time%3A%3AJulianDay/json",
    "generated": "2026-07-05T13:42:24Z",
    "synopsis": "use Time::JulianDay\n$jd = julianday($year, $month1to12, $day)\n$jd = localjulianday($secondssince1970);\n$jd = gmjulianday($secondssince1970);\n($year, $month1to12, $day) = inversejulianday($jd)\n$dow = dayofweek($jd)\nprint (Sun,Mon,Tue,Wed,Thu,Fri,Sat)[$dow];\n$secondssincejan11970 = jdsecondslocal($jd, $hour, $min, $sec)\n$secondssincejan11970 = jdsecondsgm($jd, $hour, $min, $sec)\n$secondssincejan11970 = jdtimelocal($sec,$min,$hours,$mday,$month0to11,$year)\n$secondssincejan11970 = jdtimegm($sec,$min,$hours,$mday,$month0to11,$year)",
    "sections": {
        "NAME": {
            "content": "Time::JulianDay -- Julian calendar manipulations\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "use Time::JulianDay\n\n$jd = julianday($year, $month1to12, $day)\n$jd = localjulianday($secondssince1970);\n$jd = gmjulianday($secondssince1970);\n($year, $month1to12, $day) = inversejulianday($jd)\n$dow = dayofweek($jd)\n\nprint (Sun,Mon,Tue,Wed,Thu,Fri,Sat)[$dow];\n\n$secondssincejan11970 = jdsecondslocal($jd, $hour, $min, $sec)\n$secondssincejan11970 = jdsecondsgm($jd, $hour, $min, $sec)\n$secondssincejan11970 = jdtimelocal($sec,$min,$hours,$mday,$month0to11,$year)\n$secondssincejan11970 = jdtimegm($sec,$min,$hours,$mday,$month0to11,$year)\n",
            "subsections": []
        },
        "DESCRIPTION": {
            "content": "JulianDay is a package that manipulates dates as number of days since some time a long time ago.\nIt's easy to add and subtract time using julian days...\n\nThe dayofweek returned by dayofweek() is 0 for Sunday, and 6 for Saturday and everything\nelse is in between.\n",
            "subsections": []
        },
        "ERRATA": {
            "content": "Time::JulianDay is not a correct implementation. There are two problems. The first problem is\nthat Time::JulianDay only works with integers. Julian Day can be fractional to represent time\nwithin a day. If you call inversejulianday() with a non-integer time, it will often give you\nan incorrect result.\n\nThe second problem is that Julian Days start at noon rather than midnight. The julianday()\nfunction returns results that are too large by 0.5.\n\nWhat to do about these problems is currently open for debate. I'm tempted to leave the current\nfunctions alone and add a second set with more accurate behavior.\n\nThere is another implementation in Astro::Time that may be more accurate.\n",
            "subsections": []
        },
        "GENESIS": {
            "content": "Written by David Muir Sharnoff <cpan@dave.sharnoff.org> with help from previous work by Kurt\nJaeger aka PI <zrzr0111@helpdesk.rus.uni-stuttgart.de> based on postings from: Ian Miller\n<ianm@cix.compulink.co.uk>; Gary Puckering <garyp%cognos.uucp@uunet.uu.net> based on Collected\nAlgorithms of the ACM ?; and the unknown-to-me author of Time::Local.\n",
            "subsections": []
        },
        "LICENSE": {
            "content": "Copyright (C) 1996-1999 David Muir Sharnoff. License hereby granted for anyone to use, modify or\nredistribute this module at their own risk. Please feed useful changes back to\ncpan@dave.sharnoff.org.\n",
            "subsections": []
        }
    },
    "summary": "Time::JulianDay -- Julian calendar manipulations",
    "flags": [],
    "examples": [],
    "see_also": []
}