BOOLEAN
RtlTimeToSecondsSince1980(
  IN  PLARGE_INTEGER Time,
  OUT PULONG ElapsedSeconds
  );

Routine Description:

    This routine converts an input 64-bit NT Time variable to the
    number of seconds since the start of 1980.  The NT time must be
    within the range 1980 to around 2115.

Arguments:

    Time - Supplies the Time to convert from

    ElapsedSeconds - Receives the number of seconds since the start of 1980
        denoted by Time

Return Value:

    BOOLEAN - TRUE if the input Time is within a range expressible by
        ElapsedSeconds and FALSE otherwise