How to get the difference between two QDateTimes in milliseconds?

Question

I wish QDateTime overrode the - operator and returned a QTimeSpan representing the difference between two QDateTimes (just like .NET's TimeSpan). Since this doesn't exist in Qt, I decided to implement it.

Unfortunately, QDateTime has no msecsTo-like function. What is the cleanest way to get the difference between two QDateTimes accurate to the millisecond?

Answer 1

I would probably use a.daysTo(b)*1000*60*60*24 + a.time().msecsTo(b.time()). Note that you need to watch how close you can be, since you're going to overflow your data type rather quickly.

Answer 2

how about this:

QDateTime a = QDateTime::currentDateTime();
QDateTime b = a.addMSecs( 1000 );
qDebug( "%d", a.time().msecsTo( b.time() ) );

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