refactoring of JulianDay

see issue #693

Author: MenoData

calendar/src/main/java/net/time4j/calendar/astro/JulianDay.java

@@ -22,7 +22,11 @@
 package net.time4j.calendar.astro;
 
 import net.time4j.Moment;
+import net.time4j.PlainTime;
+import net.time4j.engine.CalendarDate;
+import net.time4j.engine.EpochDays;
 import net.time4j.scale.TimeScale;
+import net.time4j.tz.ZonalOffset;
 
 import java.io.IOException;
 import java.io.ObjectInputStream;
@@ -180,6 +184,47 @@ public static JulianDay ofEphemerisTime(Moment moment) {
 
     }
 
+    /**
+     * <p>Creates a Julian day on the time scale {@link TimeScale#TT},
+     * sometimes also called <em>Julian Ephemeris Day</em>. </p>
+     *
+     * <p>This kind of Julian day represents the actual astronomical standard. The time
+     * TT-2000-01-01T12:00Z corresponds to JD(TT)2451545.0 </p>
+     *
+     * @param   date        calendar date
+     * @param   time        local time
+     * @param   offset      timezone offset
+     * @return  JulianDay
+     * @throws  IllegalArgumentException if the Julian day of moment is not in supported range
+     * @since   3.36/4.31
+     */
+    /*[deutsch]
+     * <p>Erzeugt einen julianischen Tag auf der Zeitskala {@link TimeScale#TT},
+     * manchmal auch <em>Julian Ephemeris Day</em> genannt. </p>
+     *
+     * <p>Diese Art des julianischen Tages repr&auml;sentiert den aktuellen astronomischen Standard.
+     * Die Zeit TT-2000-01-01T12:00Z entspricht JD(TT)2451545.0 </p>
+     *
+     * @param   date        calendar date
+     * @param   time        local time
+     * @param   offset      timezone offset
+     * @return  JulianDay
+     * @throws  IllegalArgumentException if the Julian day of moment is not in supported range
+     * @since   3.36/4.31
+     */
+    public static JulianDay ofEphemerisTime(
+        CalendarDate date,
+        PlainTime time,
+        ZonalOffset offset
+    ) {
+
+        long d = EpochDays.JULIAN_DAY_NUMBER.transform(date.getDaysSinceEpochUTC(), EpochDays.UTC);
+        double tod = time.get(PlainTime.NANO_OF_DAY) / (86400.0 * 1000000000L);
+        double jde = d - 0.5 + tod - offset.getIntegralAmount() / 86400.0;
+        return new JulianDay(jde, TimeScale.TT);
+
+    }
+
     /**
      * <p>Creates a Julian day on the time scale {@link TimeScale#UT},
      * hence related to the mean solar time. </p>
@@ -332,7 +377,7 @@ public double getMJD() {
      * @return  Julian century in J2000-frame
      * @since   3.36/4.31
      */
-    public double getCentury() {
+    public double getCenturyJ2000() {
 
         return (this.value - 2451545.0) / 36525;
 

calendar/src/main/java/net/time4j/calendar/astro/MoonPhase.java

@@ -331,7 +331,7 @@ public Moment atLunation(int n) {
 	 */
 	public static double getIllumination(Moment moment) {
 
-		double jct = JulianDay.ofEphemerisTime(moment).getCentury();
+		double jct = JulianDay.ofEphemerisTime(moment).getCenturyJ2000();
 
 		// Meeus (47.2)
 		double meanElongation =

calendar/src/test/java/net/time4j/calendar/astro/JulianDayTest.java

@@ -2,8 +2,13 @@
 
 import net.time4j.ClockUnit;
 import net.time4j.Moment;
+import net.time4j.PlainDate;
+import net.time4j.PlainTime;
 import net.time4j.PlainTimestamp;
+import net.time4j.engine.EpochDays;
 import net.time4j.scale.TimeScale;
+import net.time4j.tz.OffsetSign;
+import net.time4j.tz.ZonalOffset;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -18,18 +23,29 @@
 public class JulianDayTest {
 
     @Test
-    public void ephemerisTime() {
+    public void ephemerisTime1() {
         Moment j2000 = // TT = UTC + 42.184
             PlainTimestamp.of(2000, 1, 1, 11, 58, 56).minus(184, ClockUnit.MILLIS).atUTC();
         assertThat(j2000.toString(TimeScale.TT), is("TT-2000-01-01T12Z"));
         JulianDay expected = JulianDay.ofEphemerisTime(2451545.0);
         assertThat(JulianDay.ofEphemerisTime(j2000), is(expected));
         assertThat(expected.getMJD(), is(51544.5));
-        assertThat(expected.getCentury(), is(0.0));
+        assertThat(expected.getCenturyJ2000(), is(0.0));
         assertThat(expected.getScale(), is(TimeScale.TT));
         assertThat(expected.toMoment(), is(j2000));
     }
 
+    @Test
+    public void ephemerisTime2() {
+        PlainDate date = PlainDate.of(1992, 4, 12);
+        PlainTime time = PlainTime.of(2);
+        ZonalOffset utc = ZonalOffset.ofHours(OffsetSign.AHEAD_OF_UTC, 2);
+        JulianDay jdEphemeris = JulianDay.ofEphemerisTime(date, time, utc);
+        assertThat(
+            jdEphemeris,
+            is(JulianDay.ofEphemerisTime(date.get(EpochDays.JULIAN_DAY_NUMBER) - 0.5)));
+    }
+
     @Test
     public void meanSolarTime() {
         Moment j2000 = PlainTimestamp.of(2000, 1, 1, 12, 0).atUTC();

calendar/src/test/java/net/time4j/calendar/astro/MoonTest.java

@@ -2,8 +2,9 @@
 
 import net.time4j.Moment;
 import net.time4j.PlainDate;
+import net.time4j.PlainTime;
 import net.time4j.PlainTimestamp;
-import net.time4j.engine.EpochDays;
+import net.time4j.tz.ZonalOffset;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.junit.runners.JUnit4;
@@ -106,8 +107,12 @@ public void moonPhaseOfLastQuarterBefore() {
 
     @Test
     public void illuminationOfMoon() {
-        long d = PlainDate.of(1992, 4, 12).get(EpochDays.JULIAN_DAY_NUMBER);
-        Moment m = JulianDay.ofEphemerisTime(d - 0.5).toMoment();
+        Moment m =
+            JulianDay.ofEphemerisTime(
+                PlainDate.of(1992, 4, 12),
+                PlainTime.midnightAtStartOfDay(),
+                ZonalOffset.UTC
+            ).toMoment();
         assertThat(
             MoonPhase.getIllumination(m),
             is(0.68)); // Meeus (example 48.a)