datetime - Does the windows FILETIME structure include leap seconds?

Question

The FILETIME structure counts from January 1 1601 (presumably the start of that day) according to the Microsoft documentation, but does this include leap seconds?

Answer 1

The question shouldn't be if FILETIME includes leap seconds.

It should be:

Do the people, functions, and libraries, who interpret a FILETIME (i.e. FileTimeToSystemTime) include leap seconds when counting the duration?

The simple answer is "no". FileTimeToSystemTime returns seconds as 0..59.

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The simpler answer is: "of course not, how could it?".

My Windows 2000 machine doesn't know that there were 2 leap seconds added in the decade since it was released. Any interpretation it makes of a FILETIME is wrong.

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Finally, rather than relying on logic, we can determine by direct experimental observation, the answer to the posters question:

var
    systemTime: TSystemTime;
    fileTime: TFileTime;
begin
    //Construct a system-time for the 12/31/2008 11:59:59 pm
    ZeroMemory(@systemTime, SizeOf(systemTime));
    systemtime.wYear := 2008;
    systemTime.wMonth := 12;
    systemTime.wDay := 31;
    systemTime.wHour := 23;
    systemtime.wMinute := 59;
    systemtime.wSecond := 59;

    //Convert it to a file time
    SystemTimeToFileTime(systemTime, {var}fileTime);

    //There was a leap second 12/31/2008 11:59:60 pm
    //Add one second to our filetime to reach the leap second
    filetime.dwLowDateTime := fileTime.dwLowDateTime+10000000; //10,000,000 * 100ns = 1s

    //Convert the filetime, sitting on a leap second, to a displayable system time
    FileTimeToSystemTime(fileTime, {var}systemTime);

    //And now print the system time
    ShowMessage(DateTimeToStr(SystemTimeToDateTime(systemTime)));

Adding one second to

12/31/2008 11:59:59pm

gives

1/1/2009 12:00:00am

rather than

1/1/2009 11:59:60pm

Q.E.D.

Original poster might not like it, but god intentionally rigged it so that a year is not evenly divisible by a day. He did it just to screw up programmers.