2016-07-04 16:32:31 -04:00
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<head>
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<title>islamic</title>
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2023-01-07 22:56:16 +01:00
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2016-07-04 16:32:31 -04:00
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2023-01-07 22:56:16 +01:00
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2016-07-04 16:32:31 -04:00
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2023-01-07 22:56:16 +01:00
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2016-07-04 16:32:31 -04:00
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</head>
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<body>
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<address align=right>
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<br/>
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<br/>
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<a href="mailto:howard.hinnant@gmail.com">Howard E. Hinnant</a><br/>
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2016-07-04<br/>
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</address>
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<hr/>
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<h1 align=center><code>islamic</code></h1>
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<h2>Contents</h2>
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<ul>
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<li><a href="https://github.com/HowardHinnant/date">github link</a></li>
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<li><a href="#Introduction">Introduction</a></li>
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</ul>
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<a name="Introduction"></a><h2>Introduction</h2>
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<p>
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This is an Islamic calendar in the style of
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<a href="date.html">date.h</a>.
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2023-07-24 18:57:24 +01:00
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Everything is the same here as for
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<a href="date.html">date.h</a>,
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except that the calendrical arithmetic implements a proleptic
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<a href="https://en.wikipedia.org/wiki/Tabular_Islamic_calendar">Tabular Islamic calendar</a>.
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</p>
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<p>
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The <code>islamic</code> calendar can interoperate with
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<a href="date.html">date.h</a> and <a href="tz.html">tz.h</a> just by
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paying attention to the namespace. For example to convert the <i>civil</i>
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date <code>2016_y/jul/4</code> to an islamic date, just do:
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</p>
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<blockquote><pre>
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#include "islamic.h"
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#include <iostream>
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int
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main()
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{
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using namespace date::literals;
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std::cout << islamic::year_month_day{2016_y/jul/4} << '\n';
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}
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</pre></blockquote>
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<p>
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This outputs:
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</p>
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<blockquote><pre>
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1437-09-28
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</pre></blockquote>
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<p>
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And here is the reverse conversion:
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</p>
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<blockquote><pre>
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#include "islamic.h"
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#include <iostream>
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int
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main()
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{
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using namespace islamic::literals;
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std::cout << date::year_month_day{1437_y/9/28} << '\n';
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}
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</pre></blockquote>
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<p>
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Which outputs:
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</p>
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<blockquote><pre>
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2016-07-04
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</pre></blockquote>
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<p>
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You can even convert directly to the ISO-week-based calendar:
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</p>
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<blockquote><pre>
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#include "islamic.h"
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#include "iso_week.h"
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#include <iostream>
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int
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main()
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{
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using namespace islamic::literals;
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std::cout << iso_week::year_weeknum_weekday{2016_y/jun/13} << '\n';
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}
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</pre></blockquote>
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<p>
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Which outputs:
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</p>
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<blockquote><pre>
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2016-W27-Mon
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</pre></blockquote>
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<p>
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<p>
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You can find the current local islamic date and time with:
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</p>
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<blockquote><pre>
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#include "islamic.h"
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#include "tz.h"
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#include <iostream>
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int
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main()
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{
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auto zt = date::make_zoned(date::current_zone(), std::chrono::system_clock::now());
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auto ld = date::floor<date::days>(zt.get_local_time());
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2016-07-04 16:33:59 -04:00
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islamic::year_month_day ymd{ld};
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2016-07-04 16:32:31 -04:00
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auto time = date::make_time(zt.get_local_time() - ld);
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std::cout << ymd << ' ' << time << '\n';
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}
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</pre></blockquote>
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<p>
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Example output:
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</p>
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<blockquote><pre>
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1437-09-28 16:24:56.578240
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</pre></blockquote>
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<p>
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This calendar assumes that the Islamic day starts at midnight, like the civil
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calendar. This is because the only thing that is customized to the Islamic
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calendar is the calendar itself (days precision time keeping). For time-keeping
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finer than days, the <code><chrono></code> library is still in use. The
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Islamic calendar simply converts to and from <code>sys_days</code> (a
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days-precision <code>std::chrono::time_point</code>) like every other calendar.
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</p>
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</body>
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</html>
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