### Question:
Day extends RegularTimePeriod implements Serializable { @Override public long getSerialIndex() { return this.serialDate.toSerial(); } Day();  Day(int day, int month, int year);  Day(SerialDate serialDate);  Day(Date time);  Day(Date time, TimeZone zone, Locale locale); SerialDate getSerialDate(); int getYear(); int getMonth(); int getDayOfMonth(); @Override long getFirstMillisecond(); @Override long getLastMillisecond(); @Override void peg(Calendar calendar); @Override RegularTimePeriod previous(); @Override RegularTimePeriod next(); @Override long getSerialIndex(); @Override long getFirstMillisecond(Calendar calendar); @Override long getLastMillisecond(Calendar calendar); @Override boolean equals(Object obj); @Override int hashCode(); @Override int compareTo(TimePeriod o1); @Override String toString(); static Day parseDay(String s);  }### Answer:
@Test public void testGetSerialIndex() { Day d = new Day(1, 1, 1900); assertEquals(2, d.getSerialIndex()); d = new Day(15, 4, 2000); assertEquals(36631, d.getSerialIndex()); }