Conversion from WTime to WDate and vice versa does not work.
To fix this, the following OLE-functions can be used:

WTime  time;
WDate  date;
::SystemTimeToVariantTime( (const SYSTEMTIME *)&time, &date );
::VariantTimeToSystemTime( date, (SYSTEMTIME *)&time );

The functions are prototyped in oleauto.h, which is included with windows.h.
Also the oleaut32.lib must be added to project.

// Code added here will be included at the top of the .CPP file
#pragma library("oleaut32.lib")

In both functions the milliseconds are cut off. To avoid it, the following portable conversion can be used:

#include <math.h>

static const WDouble WDateMillisecondsADay = 24. * 60. * 60. * 1000.;

void TimeToDate( const WTime & time, WDate & date )
{
  ::SystemTimeToVariantTime(( const SYSTEMTIME *)&time, &date );
  date += ( WDouble( time.milliSeconds ) / WDateMillisecondsADay);
}

void DateToTime( WDate date, WTime & time )
{
  ::VariantTimeToSystemTime(date, (SYSTEMTIME *)&time) ;
  WDouble integral;
  WDouble fractional = modf( date, &integral );
  time.milliSeconds  = WShort( WLong( floor( fractional * WDateMillisecondsADay + .5) ) % 1000);
}

The bug exists in Power 2.5 beta, 2.1 and probably in all previous versions.