I used RTimer with CActive and I want to use setactive event in special time then I used this code iRTimer.At(TTime) ;
The diffrence between HomeTime and special time is 1 hour
but before that time event occure the code come in below :

void CMyTimer::Set ( TTime time )
{
Cancel() ;
iTimer.At ( iStatus , time ) ;
SetActive() ;
}

{
TTime t;
t.HomeTime() ;
TTimeIntervalMinutes interval(60);
t+=interval;
Set(t) ;
}

I understand that iTimer.At work carefully when diffrence between HomeTime and special time is maximum 30 minute
Why?