gistfile1.txt

public static int getSecondsToDayHour(Date fromDate, int hour) {
        Calendar cal = Calendar.getInstance();

        cal.set(Calendar.HOUR_OF_DAY, hour);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);

        long seconds = (cal.getTime().getTime() - fromDate.getTime()) / 1000;
        if (seconds < 0) {
            cal.add(Calendar.DATE, 1);
            seconds = (cal.getTime().getTime() - fromDate.getTime()) / 1000;
        }

        if (seconds > 24 * 60 * 60) {
            throw new ProgramLogicException(String.format("Seconds result is incorrect: %s.", seconds));
        }

        return (int) seconds;
    }

gistfile2.txt

@Test
    public void test_getSecondsToDayHour() {
        Calendar cal = Calendar.getInstance();

        cal.set(Calendar.HOUR_OF_DAY, 22);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);

        assertEquals(12 * 60 * 60, DateUtils.getSecondsToDayHour(cal.getTime(), 10));

        cal.set(Calendar.HOUR_OF_DAY, 7);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);

        assertEquals(3 * 60 * 60, DateUtils.getSecondsToDayHour(cal.getTime(), 10));
        
        assertEquals(23 * 60 * 60, DateUtils.getSecondsToDayHour(cal.getTime(), 6));
    }