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<title>SRFI-19 Time/Date conversions (Guile Reference Manual)</title>
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<div class="subsubsection-level-extent" id="SRFI_002d19-Time_002fDate-conversions">
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<p>
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Next: <a href="SRFI_002d19-Date-to-string.html" accesskey="n" rel="next">SRFI-19 Date to string</a>, Previous: <a href="SRFI_002d19-Date.html" accesskey="p" rel="prev">SRFI-19 Date</a>, Up: <a href="SRFI_002d19.html" accesskey="u" rel="up">SRFI-19 - Time/Date Library</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<h4 class="subsubsection" id="SRFI_002d19-Time_002fDate-conversions-1"><span>7.5.16.4 SRFI-19 Time/Date conversions<a class="copiable-link" href="#SRFI_002d19-Time_002fDate-conversions-1"> ¶</a></span></h4>
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<a class="index-entry-id" id="index-time-conversion"></a>
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<a class="index-entry-id" id="index-date-conversion"></a>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-date_002d_003ejulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">date->julian-day</strong> <var class="def-var-arguments">date</var><a class="copiable-link" href="#index-date_002d_003ejulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-date_002d_003emodified_002djulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">date->modified-julian-day</strong> <var class="def-var-arguments">date</var><a class="copiable-link" href="#index-date_002d_003emodified_002djulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-date_002d_003etime_002dmonotonic"><span class="category-def">Function: </span><span><strong class="def-name">date->time-monotonic</strong> <var class="def-var-arguments">date</var><a class="copiable-link" href="#index-date_002d_003etime_002dmonotonic"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-date_002d_003etime_002dtai"><span class="category-def">Function: </span><span><strong class="def-name">date->time-tai</strong> <var class="def-var-arguments">date</var><a class="copiable-link" href="#index-date_002d_003etime_002dtai"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-date_002d_003etime_002dutc"><span class="category-def">Function: </span><span><strong class="def-name">date->time-utc</strong> <var class="def-var-arguments">date</var><a class="copiable-link" href="#index-date_002d_003etime_002dutc"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-julian_002dday_002d_003edate"><span class="category-def">Function: </span><span><strong class="def-name">julian-day->date</strong> <var class="def-var-arguments">jdn [tz-offset]</var><a class="copiable-link" href="#index-julian_002dday_002d_003edate"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-julian_002dday_002d_003etime_002dmonotonic"><span class="category-def">Function: </span><span><strong class="def-name">julian-day->time-monotonic</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-julian_002dday_002d_003etime_002dmonotonic"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-julian_002dday_002d_003etime_002dtai"><span class="category-def">Function: </span><span><strong class="def-name">julian-day->time-tai</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-julian_002dday_002d_003etime_002dtai"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-julian_002dday_002d_003etime_002dutc"><span class="category-def">Function: </span><span><strong class="def-name">julian-day->time-utc</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-julian_002dday_002d_003etime_002dutc"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-modified_002djulian_002dday_002d_003edate"><span class="category-def">Function: </span><span><strong class="def-name">modified-julian-day->date</strong> <var class="def-var-arguments">jdn [tz-offset]</var><a class="copiable-link" href="#index-modified_002djulian_002dday_002d_003edate"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-modified_002djulian_002dday_002d_003etime_002dmonotonic"><span class="category-def">Function: </span><span><strong class="def-name">modified-julian-day->time-monotonic</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-modified_002djulian_002dday_002d_003etime_002dmonotonic"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-modified_002djulian_002dday_002d_003etime_002dtai"><span class="category-def">Function: </span><span><strong class="def-name">modified-julian-day->time-tai</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-modified_002djulian_002dday_002d_003etime_002dtai"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-modified_002djulian_002dday_002d_003etime_002dutc"><span class="category-def">Function: </span><span><strong class="def-name">modified-julian-day->time-utc</strong> <var class="def-var-arguments">jdn</var><a class="copiable-link" href="#index-modified_002djulian_002dday_002d_003etime_002dutc"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-time_002dmonotonic_002d_003edate"><span class="category-def">Function: </span><span><strong class="def-name">time-monotonic->date</strong> <var class="def-var-arguments">time [tz-offset]</var><a class="copiable-link" href="#index-time_002dmonotonic_002d_003edate"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dmonotonic_002d_003etime_002dtai"><span class="category-def">Function: </span><span><strong class="def-name">time-monotonic->time-tai</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dmonotonic_002d_003etime_002dtai"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dmonotonic_002d_003etime_002dtai_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-monotonic->time-tai!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dmonotonic_002d_003etime_002dtai_0021"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dmonotonic_002d_003etime_002dutc"><span class="category-def">Function: </span><span><strong class="def-name">time-monotonic->time-utc</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dmonotonic_002d_003etime_002dutc"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dmonotonic_002d_003etime_002dutc_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-monotonic->time-utc!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dmonotonic_002d_003etime_002dutc_0021"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-time_002dtai_002d_003edate"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->date</strong> <var class="def-var-arguments">time [tz-offset]</var><a class="copiable-link" href="#index-time_002dtai_002d_003edate"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003ejulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->julian-day</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003ejulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003emodified_002djulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->modified-julian-day</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003emodified_002djulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003etime_002dmonotonic"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->time-monotonic</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003etime_002dmonotonic"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003etime_002dmonotonic_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->time-monotonic!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003etime_002dmonotonic_0021"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003etime_002dutc"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->time-utc</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003etime_002dutc"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dtai_002d_003etime_002dutc_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-tai->time-utc!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dtai_002d_003etime_002dutc_0021"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn first-defun-alias-first-deffn">
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<dt class="deffn defun-alias-deffn" id="index-time_002dutc_002d_003edate"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->date</strong> <var class="def-var-arguments">time [tz-offset]</var><a class="copiable-link" href="#index-time_002dutc_002d_003edate"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003ejulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->julian-day</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003ejulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003emodified_002djulian_002dday"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->modified-julian-day</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003emodified_002djulian_002dday"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003etime_002dmonotonic"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->time-monotonic</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003etime_002dmonotonic"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003etime_002dmonotonic_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->time-monotonic!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003etime_002dmonotonic_0021"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003etime_002dtai"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->time-tai</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003etime_002dtai"> ¶</a></span></dt>
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<dt class="deffnx defunx-alias-deffnx def-cmd-deffn" id="index-time_002dutc_002d_003etime_002dtai_0021"><span class="category-def">Function: </span><span><strong class="def-name">time-utc->time-tai!</strong> <var class="def-var-arguments">time</var><a class="copiable-link" href="#index-time_002dutc_002d_003etime_002dtai_0021"> ¶</a></span></dt>
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<dd><br>
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<p>Convert between dates, times and days of the respective types. For
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instance <code class="code">time-tai->time-utc</code> accepts a <var class="var">time</var> object of type
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<code class="code">time-tai</code> and returns an object of type <code class="code">time-utc</code>.
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</p>
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<p>The <code class="code">!</code> variants may modify their <var class="var">time</var> argument to form
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their return. The plain functions create a new object.
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</p>
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<p>For conversions to dates, <var class="var">tz-offset</var> is seconds east of
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Greenwich. The default is the local timezone, at the given time, as
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provided by the system, using <code class="code">localtime</code> (see <a class="pxref" href="Time.html">Time</a>).
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</p>
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<p>On 32-bit systems, <code class="code">localtime</code> is limited to a 32-bit
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<code class="code">time_t</code>, so a default <var class="var">tz-offset</var> is only available for
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times between Dec 1901 and Jan 2038. For prior dates an application
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might like to use the value in 1902, though some locations have zone
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changes prior to that. For future dates an application might like to
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assume today’s rules extend indefinitely. But for correct daylight
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savings transitions it will be necessary to take an offset for the
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same day and time but a year in range and which has the same starting
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weekday and same leap/non-leap (to support rules like last Sunday in
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October).
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</p></dd></dl>
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Next: <a href="SRFI_002d19-Date-to-string.html">SRFI-19 Date to string</a>, Previous: <a href="SRFI_002d19-Date.html">SRFI-19 Date</a>, Up: <a href="SRFI_002d19.html">SRFI-19 - Time/Date Library</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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