### Question:
Day extends RegularTimePeriod implements Serializable { @Override public long getFirstMillisecond() { return this.firstMillisecond; } 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 testGetFirstMillisecond() { Locale saved = Locale.getDefault(); Locale.setDefault(Locale.UK); TimeZone savedZone = TimeZone.getDefault(); TimeZone.setDefault(TimeZone.getTimeZone("Europe/London")); Day d = new Day(1, 3, 1970); assertEquals(5094000000L, d.getFirstMillisecond()); Locale.setDefault(saved); TimeZone.setDefault(savedZone); }
@Test public void testGetFirstMillisecondWithTimeZone() { Day d = new Day(26, 4, 1950); TimeZone zone = TimeZone.getTimeZone("America/Los_Angeles"); Calendar c = new GregorianCalendar(zone); assertEquals(-621187200000L, d.getFirstMillisecond(c)); try { d.getFirstMillisecond(null); fail("NullPointerException should have been thrown"); } catch (NullPointerException e) { } }
@Test public void testGetFirstMillisecondWithCalendar() { Day d = new Day(1, 12, 2001); GregorianCalendar calendar = new GregorianCalendar(Locale.GERMANY); calendar.setTimeZone(TimeZone.getTimeZone("Europe/Frankfurt")); assertEquals(1007164800000L, d.getFirstMillisecond(calendar)); try { d.getFirstMillisecond(null); fail("NullPointerException should have been thrown"); } catch (NullPointerException e) { } }