 <p>The reason to use a double here is the attempt to provide enough accuracy. </p> <p>In detail: The systems interrupt time slices are given by <em>ActualResolution</em> which is returned by <code>NtQueryTimerResolution()</code>. NtQueryTimerResolution is exported by the native Windows NT library NTDLL.DLL. The System time increments are given by <em>TimeIncrement</em> which is returned by <code>GetSystemTimeAdjustment()</code>.</p> <p>These two values are determining the behavior of the system timers. They are integer values and the express 100 ns units. However, this is already insufficient for certain hardware today. On some systems <em>ActualResolution</em> is returned 9766 which would correspond to 0.9766 ms. But in fact these systems are operating at 1024 interrupts per second (tuned by proper setting of the multimedia interface). 1024 interrupts a second will cause the interrupt period to be 0.9765625 ms. This is of too high detail, it reaches into the 100 ps regime and can therefore not be hold in the standard <em>ActualResolution</em> format.</p> <p>Therefore it has been decided to put such time-parameters into double. But: This does <strong>not</strong> mean that all of the posible values are supported/used. The granularity given by <em>TimeIncrement</em> will persist, no matter what.</p> <p>When dealing with timers it is always advisable to look at the granularity of the parameters involved.</p> <p>So back to your question: <code>Can Interval support values like 5.768585 (ms) ?</code></p> <p><strong>No</strong>, the system I've taken as an example above cannot.</p> <p><strong>But it can support 5.859375 (ms)!</strong></p> <p>Other systems with different hardware may support other numbers.</p> <p>So the idea of introducing a double here is not such a stupid idea and actually makes sense. Spending another 4 bytes to get things finally right is a good investment.</p> <p>I've summarized some more details about Windows time matters <a href="http://www.windowstimestamp.com/description" rel="nofollow">here</a>.</p>