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<p>A collection of methods around date/time values.
<a href="class_qwt_date.html#details">More...</a></p>
<p><code>#include <<a class="el" href="qwt__date_8h_source.html">qwt_date.h</a>></code></p>
<table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-types"></a>
Public Types</h2></td></tr>
<tr class="memitem:ab915db512c556a4666ada4fbfccfce1e"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a> { <a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1ea82971cd90d670fe3048ad8c377379c1d">FirstThursday</a>,
<a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1eab5c50b8108f8c4535201c0c590a598d6">FirstDay</a>
}</td></tr>
<tr class="separator:ab915db512c556a4666ada4fbfccfce1e"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ad037b999a51cae4d9ab36bf8e7859587"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">IntervalType</a> { <br />
  <a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587a4e1d45d6382c27689a30adc11186d4f1">Millisecond</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587aabaf7a7d45288a33590f61fe075b3590">Second</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587a7c9073c66b2628adbe772ac4c1a678ef">Minute</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587a8e7a2f91f89423e446bfdaa1e01ebd2f">Hour</a>,
<br />
  <a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587a1d503616cab082a9c741be881cc0a813">Day</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587ae204b4e8ce8679ba9ac378e41bd77b2b">Week</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587a0ab43f35f1bdbae7536be2be0455700a">Month</a>,
<a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587ae306523ed94ccf930afb811ff7a735ab">Year</a>
<br />
}</td></tr>
<tr class="separator:ad037b999a51cae4d9ab36bf8e7859587"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:af636fffdebea2e4463fc32461b1217e0"><td class="memItemLeft" align="right" valign="top">enum  </td><td class="memItemRight" valign="bottom">{ <a class="el" href="class_qwt_date.html#af636fffdebea2e4463fc32461b1217e0aed8ee8f3dbc5b7a5e953b3ec51a79108">JulianDayForEpoch</a> = 2440588
}</td></tr>
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</table><table class="memberdecls">
<tr class="heading"><td colspan="2"><h2 class="groupheader"><a name="pub-static-methods"></a>
Static Public Member Functions</h2></td></tr>
<tr class="memitem:a9ab1845543957472c2c6529ad03ef98d"><td class="memItemLeft" align="right" valign="top">static QDate </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#a9ab1845543957472c2c6529ad03ef98d">minDate</a> ()</td></tr>
<tr class="separator:a9ab1845543957472c2c6529ad03ef98d"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:af82ba26011550602f1adb61da53bd830"><td class="memItemLeft" align="right" valign="top">static QDate </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#af82ba26011550602f1adb61da53bd830">maxDate</a> ()</td></tr>
<tr class="separator:af82ba26011550602f1adb61da53bd830"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a8039dc115458981fc1c7fc2c0aa8d053"><td class="memItemLeft" align="right" valign="top">static QDateTime </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#a8039dc115458981fc1c7fc2c0aa8d053">toDateTime</a> (double value, Qt::TimeSpec=Qt::UTC)</td></tr>
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<tr class="memitem:afce10fd70f7a1ecac3f97776fb2dc46a"><td class="memItemLeft" align="right" valign="top">static double </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#afce10fd70f7a1ecac3f97776fb2dc46a">toDouble</a> (const QDateTime &)</td></tr>
<tr class="separator:afce10fd70f7a1ecac3f97776fb2dc46a"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:ab4d7b043971e13a97a8b5f9edb5eee02"><td class="memItemLeft" align="right" valign="top">static QDateTime </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#ab4d7b043971e13a97a8b5f9edb5eee02">ceil</a> (const QDateTime &, <a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">IntervalType</a>)</td></tr>
<tr class="separator:ab4d7b043971e13a97a8b5f9edb5eee02"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a1b350f22a57b44b529bc4de740dbe213"><td class="memItemLeft" align="right" valign="top">static QDateTime </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#a1b350f22a57b44b529bc4de740dbe213">floor</a> (const QDateTime &, <a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">IntervalType</a>)</td></tr>
<tr class="separator:a1b350f22a57b44b529bc4de740dbe213"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:abb91fb441a254337d5445ad4bab1a662"><td class="memItemLeft" align="right" valign="top">static QDate </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#abb91fb441a254337d5445ad4bab1a662">dateOfWeek0</a> (int year, <a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a>)</td></tr>
<tr class="memdesc:abb91fb441a254337d5445ad4bab1a662"><td class="mdescLeft"> </td><td class="mdescRight">Date of the first day of the first week for a year. <a href="#abb91fb441a254337d5445ad4bab1a662">More...</a><br /></td></tr>
<tr class="separator:abb91fb441a254337d5445ad4bab1a662"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a90dd1f9dc38565c003f8e1ef821965b7"><td class="memItemLeft" align="right" valign="top">static int </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#a90dd1f9dc38565c003f8e1ef821965b7">weekNumber</a> (const QDate &, <a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a>)</td></tr>
<tr class="separator:a90dd1f9dc38565c003f8e1ef821965b7"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:aeadce3496f631eae3a7e54749078c7a4"><td class="memItemLeft" align="right" valign="top">static int </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#aeadce3496f631eae3a7e54749078c7a4">utcOffset</a> (const QDateTime &)</td></tr>
<tr class="separator:aeadce3496f631eae3a7e54749078c7a4"><td class="memSeparator" colspan="2"> </td></tr>
<tr class="memitem:a2c19998281321ba078d717f7f9ec6855"><td class="memItemLeft" align="right" valign="top">static QString </td><td class="memItemRight" valign="bottom"><a class="el" href="class_qwt_date.html#a2c19998281321ba078d717f7f9ec6855">toString</a> (const QDateTime &, const QString &format, <a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a>)</td></tr>
<tr class="separator:a2c19998281321ba078d717f7f9ec6855"><td class="memSeparator" colspan="2"> </td></tr>
</table>
<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>A collection of methods around date/time values. </p>
<p>Qt offers convenient classes for dealing with date/time values, but Qwt uses coordinate systems that are based on doubles. <a class="el" href="class_qwt_date.html" title="A collection of methods around date/time values. ">QwtDate</a> offers methods to translate from QDateTime to double and v.v.</p>
<p>A double is interpreted as the number of milliseconds since 1970-01-01T00:00:00 Universal Coordinated Time - also known as "The Epoch".</p>
<p>While the range of the Julian day in Qt4 is limited to [0, MAX_INT], Qt5 stores it as qint64 offering a huge range of valid dates. As the significance of a double is below this ( assuming a fraction of 52 bits ) the translation is not bijective with rounding errors for dates very far from Epoch. For a resolution of 1 ms those start to happen for dates above the year 144683.</p>
<p>An axis for a date/time interval is expected to be aligned and divided in time/date units like seconds, minutes, ... <a class="el" href="class_qwt_date.html" title="A collection of methods around date/time values. ">QwtDate</a> offers several algorithms that are needed to calculate these axes.</p>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date_scale_engine.html" title="A scale engine for date/time values. ">QwtDateScaleEngine</a>, <a class="el" href="class_qwt_date_scale_draw.html" title="A class for drawing datetime scales. ">QwtDateScaleDraw</a>, QDate, QTime </dd></dl>
</div><h2 class="groupheader">Member Enumeration Documentation</h2>
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<td class="memname">anonymous enum</td>
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<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a class="anchor" id="af636fffdebea2e4463fc32461b1217e0aed8ee8f3dbc5b7a5e953b3ec51a79108"></a>JulianDayForEpoch </td><td class="fielddoc">
<p>The Julian day of "The Epoch". </p>
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<td class="memname">enum <a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">QwtDate::IntervalType</a></td>
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<p>Classification of an time interval</p>
<p>Time intervals needs to be classified to decide how to align and divide it. </p>
<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587a4e1d45d6382c27689a30adc11186d4f1"></a>Millisecond </td><td class="fielddoc">
<p>The interval is related to milliseconds. </p>
</td></tr>
<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587aabaf7a7d45288a33590f61fe075b3590"></a>Second </td><td class="fielddoc">
<p>The interval is related to seconds. </p>
</td></tr>
<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587a7c9073c66b2628adbe772ac4c1a678ef"></a>Minute </td><td class="fielddoc">
<p>The interval is related to minutes. </p>
</td></tr>
<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587a8e7a2f91f89423e446bfdaa1e01ebd2f"></a>Hour </td><td class="fielddoc">
<p>The interval is related to hours. </p>
</td></tr>
<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587a1d503616cab082a9c741be881cc0a813"></a>Day </td><td class="fielddoc">
<p>The interval is related to days. </p>
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<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587ae204b4e8ce8679ba9ac378e41bd77b2b"></a>Week </td><td class="fielddoc">
<p>The interval is related to weeks. </p>
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<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587a0ab43f35f1bdbae7536be2be0455700a"></a>Month </td><td class="fielddoc">
<p>The interval is related to months. </p>
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<tr><td class="fieldname"><a class="anchor" id="ad037b999a51cae4d9ab36bf8e7859587ae306523ed94ccf930afb811ff7a735ab"></a>Year </td><td class="fielddoc">
<p>The interval is related to years. </p>
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<td class="memname">enum <a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">QwtDate::Week0Type</a></td>
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<p>How to identify the first week of year differs between countries. </p>
<table class="fieldtable">
<tr><th colspan="2">Enumerator</th></tr><tr><td class="fieldname"><a class="anchor" id="ab915db512c556a4666ada4fbfccfce1ea82971cd90d670fe3048ad8c377379c1d"></a>FirstThursday </td><td class="fielddoc">
<p>According to ISO 8601 the first week of a year is defined as "the week with the year's first Thursday in it".</p>
<p>FirstThursday corresponds to the numbering that is implemented in QDate::weekNumber(). </p>
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<tr><td class="fieldname"><a class="anchor" id="ab915db512c556a4666ada4fbfccfce1eab5c50b8108f8c4535201c0c590a598d6"></a>FirstDay </td><td class="fielddoc">
<p>"The week with January 1.1 in it."</p>
<p>In the U.S. this definition is more common than FirstThursday. </p>
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<h2 class="groupheader">Member Function Documentation</h2>
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<td class="memname">QDateTime QwtDate::ceil </td>
<td>(</td>
<td class="paramtype">const QDateTime & </td>
<td class="paramname"><em>dateTime</em>, </td>
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<td class="paramkey"></td>
<td></td>
<td class="paramtype"><a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">IntervalType</a> </td>
<td class="paramname"><em>intervalType</em> </td>
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<td>)</td>
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<p>Ceil a datetime according the interval type</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">dateTime</td><td>Datetime value </td></tr>
<tr><td class="paramname">intervalType</td><td>Interval type, how to ceil. F.e. when intervalType = QwtDate::Months, the result will be ceiled to the next beginning of a month </td></tr>
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</dd>
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<dl class="section return"><dt>Returns</dt><dd>Ceiled datetime </dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#a1b350f22a57b44b529bc4de740dbe213">floor()</a> </dd></dl>
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<td>(</td>
<td class="paramtype">int </td>
<td class="paramname"><em>year</em>, </td>
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<td class="paramkey"></td>
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<td class="paramname"><em>type</em> </td>
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<p>Date of the first day of the first week for a year. </p>
<p>The first day of a week depends on the current locale ( QLocale::firstDayOfWeek() ).</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">year</td><td>Year </td></tr>
<tr><td class="paramname">type</td><td>Option how to identify the first week </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>First day of week 0</dd></dl>
<dl class="section see"><dt>See also</dt><dd>QLocale::firstDayOfWeek(), <a class="el" href="class_qwt_date.html#a90dd1f9dc38565c003f8e1ef821965b7">weekNumber()</a> </dd></dl>
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<td class="memname">QDateTime QwtDate::floor </td>
<td>(</td>
<td class="paramtype">const QDateTime & </td>
<td class="paramname"><em>dateTime</em>, </td>
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<td class="paramtype"><a class="el" href="class_qwt_date.html#ad037b999a51cae4d9ab36bf8e7859587">IntervalType</a> </td>
<td class="paramname"><em>intervalType</em> </td>
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<p>Floor a datetime according the interval type</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">dateTime</td><td>Datetime value </td></tr>
<tr><td class="paramname">intervalType</td><td>Interval type, how to ceil. F.e. when intervalType = QwtDate::Months, the result will be ceiled to the next beginning of a month </td></tr>
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</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>Floored datetime </dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#a1b350f22a57b44b529bc4de740dbe213">floor()</a> </dd></dl>
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<td class="memname">QDate QwtDate::maxDate </td>
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<p>Maximum for the supported date range</p>
<p>The range of valid dates depends on how QDate stores the Julian day internally.</p>
<ul>
<li>For Qt4 it is "Tue Jun 3 5874898"</li>
<li>For Qt5 it is "Tue Dec 31 2147483647"</li>
</ul>
<dl class="section return"><dt>Returns</dt><dd>maximum of the date range </dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#a9ab1845543957472c2c6529ad03ef98d">minDate()</a> </dd></dl>
<dl class="section note"><dt>Note</dt><dd>The maximum differs between Qt4 and Qt5 </dd></dl>
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<td class="memname">QDate QwtDate::minDate </td>
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<p>Minimum for the supported date range</p>
<p>The range of valid dates depends on how QDate stores the Julian day internally.</p>
<ul>
<li>For Qt4 it is "Tue Jan 2 -4713"</li>
<li>For Qt5 it is "Thu Jan 1 -2147483648"</li>
</ul>
<dl class="section return"><dt>Returns</dt><dd>minimum of the date range </dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#af82ba26011550602f1adb61da53bd830">maxDate()</a> </dd></dl>
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<td class="memname">QDateTime QwtDate::toDateTime </td>
<td>(</td>
<td class="paramtype">double </td>
<td class="paramname"><em>value</em>, </td>
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<td class="paramtype">Qt::TimeSpec </td>
<td class="paramname"><em>timeSpec</em> = <code>Qt::UTC</code> </td>
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<p>Translate from double to QDateTime</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">value</td><td>Number of milliseconds since the epoch, 1970-01-01T00:00:00 UTC </td></tr>
<tr><td class="paramname">timeSpec</td><td>Time specification </td></tr>
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<dl class="section return"><dt>Returns</dt><dd>Datetime value</dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#afce10fd70f7a1ecac3f97776fb2dc46a">toDouble()</a>, QDateTime::setMSecsSinceEpoch() </dd></dl>
<dl class="section note"><dt>Note</dt><dd>The return datetime for Qt::OffsetFromUTC will be Qt::UTC </dd></dl>
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<td class="memname">double QwtDate::toDouble </td>
<td>(</td>
<td class="paramtype">const QDateTime & </td>
<td class="paramname"><em>dateTime</em></td><td>)</td>
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<p>Translate from QDateTime to double</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">dateTime</td><td>Datetime value </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>Number of milliseconds since 1970-01-01T00:00:00 UTC has passed.</dd></dl>
<dl class="section see"><dt>See also</dt><dd><a class="el" href="class_qwt_date.html#a8039dc115458981fc1c7fc2c0aa8d053">toDateTime()</a>, QDateTime::toMSecsSinceEpoch() </dd></dl>
<dl class="section warning"><dt>Warning</dt><dd>For values very far below or above 1970-01-01 UTC rounding errors will happen due to the limited significance of a double. </dd></dl>
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<td>(</td>
<td class="paramtype">const QDateTime & </td>
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<td class="paramtype">const QString & </td>
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<td class="paramtype"><a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a> </td>
<td class="paramname"><em>week0Type</em> </td>
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<p>Translate a datetime into a string</p>
<p>Beside the format expressions documented in QDateTime::toString() the following expressions are supported:</p>
<ul>
<li>w<br />
week number: ( 1 - 53 )</li>
<li>ww<br />
week number with a leading zero ( 01 - 53 )</li>
</ul>
<p>As week 1 usually starts in the previous year a special rule is applied for formats, where the year is expected to match the week number - even if the date belongs to the previous year.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">dateTime</td><td>Datetime value </td></tr>
<tr><td class="paramname">format</td><td>Format string </td></tr>
<tr><td class="paramname">week0Type</td><td>Specification of week 0</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>Datetime string </dd></dl>
<dl class="section see"><dt>See also</dt><dd>QDateTime::toString(), <a class="el" href="class_qwt_date.html#a90dd1f9dc38565c003f8e1ef821965b7">weekNumber()</a>, <a class="el" href="class_qwt_date_scale_draw.html" title="A class for drawing datetime scales. ">QwtDateScaleDraw</a> </dd></dl>
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<td class="memname">int QwtDate::utcOffset </td>
<td>(</td>
<td class="paramtype">const QDateTime & </td>
<td class="paramname"><em>dateTime</em></td><td>)</td>
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<p>Offset in seconds from Coordinated Universal Time</p>
<p>The offset depends on the time specification of dateTime:</p>
<ul>
<li>Qt::UTC 0, dateTime has no offset</li>
<li>Qt::OffsetFromUTC returns dateTime.utcOffset()</li>
<li>Qt::LocalTime: number of seconds from the UTC</li>
</ul>
<p>For Qt::LocalTime the offset depends on the timezone and daylight savings.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">dateTime</td><td>Datetime value </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>Offset in seconds </dd></dl>
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<td class="memname">int QwtDate::weekNumber </td>
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<td class="paramtype">const QDate & </td>
<td class="paramname"><em>date</em>, </td>
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<td class="paramtype"><a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1e">Week0Type</a> </td>
<td class="paramname"><em>type</em> </td>
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<p>Find the week number of a date</p>
<ul>
<li><a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1ea82971cd90d670fe3048ad8c377379c1d">QwtDate::FirstThursday</a><br />
Corresponding to ISO 8601 ( see QDate::weekNumber() ).</li>
<li><a class="el" href="class_qwt_date.html#ab915db512c556a4666ada4fbfccfce1eab5c50b8108f8c4535201c0c590a598d6">QwtDate::FirstDay</a><br />
Number of weeks that have begun since <a class="el" href="class_qwt_date.html#abb91fb441a254337d5445ad4bab1a662" title="Date of the first day of the first week for a year. ">dateOfWeek0()</a>.</li>
</ul>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">date</td><td>Date </td></tr>
<tr><td class="paramname">type</td><td>Option how to identify the first week</td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>Week number, starting with 1 </dd></dl>
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