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<p><a href="../index.html"><img src="title-21.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.1" border="0"></a>
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<p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>:
Date/time: </p>
<ul>
<li>
<h5><a href="time.datetime.html">Datetime type</a></h5>
</li>
<li>
<h5><a href="time.calendar.html">Date/calendar manipulation</a></h5>
</li>
<li>
<h5><a href="time.time.html">Time manipulation</a></h5>
</li>
</ul>
<p>The <span class="lang">datetime</span> data type and the accompanying utilities
provide portable (system-independent) means of calendar and time manipulation.
<span class="lang">Datetime</span> is equivalent to signed 64-bit integer type
(<span class="lang">large</span> type in PTypes) which holds a time value with
a millisecond precision in the range of dates 01/01/0001 through 12/31/9999. The
value of a datetime variable represents the number of milliseconds since the beginning
of the calendar, i.e. midnight January 1st, year 1. The upper limit is caused
by the fact that the leap year rule may (and most likely will) change after the
year 10000.</p>
<p>Variables of type <span class="lang">datetime</span> can be used in various
ways: as a date/time stamp, as a difference between two events in the range from
1 millisecond up to 10,000 years, as a date alone without the time (e.g. for calendar
manipulation), and as a time value alone.</p>
<p>The date/time manipulation functions are divided into 3 groups in this documentation:
<a href="time.datetime.html">general</a>, <a href="time.calendar.html">date/calendar</a>
and <a href="time.time.html">time</a>. Most of these functions work with parameters
of type <span class="lang">datetime</span>. The prototypes and other declarations
are in the header file <a href="include/ptime.h.html"><ptime.h></a>. </p>
<p>Here are some examples of using <span class="lang">datetime</span> and the
accompanying utilities:</p>
<blockquote>
<pre>#include <pasync.h> <span class="comment">// for psleep()</span>
#include <ptime.h>
#include <pstreams.h>
USING_PTYPES
int main()
{
<span class="comment">// PTypes' birthday (birth moment, if you wish)</span>
datetime d = encodedate(2000, 3, 30) + encodetime(13, 24, 58, 995);
<span class="comment">// The format specifier %t is for timestamps</span>
pout.putf("PTypes' birth moment: %t\n", d);
<span class="comment">// now see how old is PTypes in milliseconds</span>
datetime diff = now() - d;
int hours, mins, secs, msecs;
decodetime(diff, hours, mins, secs, msecs);
pout.putf("PTypes' life time: %d hours %d minutes %d seconds and %d milliseconds\n",
days(diff) * 24 + hours, mins, secs, msecs);
<span class="comment">// measure the difference in milliseconds between two calls to now()</span>
datetime m = now();
psleep(17); <span class="comment">// sleep 17 milliseconds</span>
pout.putf("A 17 millisecond dream lasted actually %d milliseconds\n", now() - m);
<span class="comment">// this will show the actual precision of the clock on the given platform;
// Windows, f.ex., always shows the difference in 10 msec increments</span>
}
</pre>
</blockquote>
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