Calculate closest date/time to raw value

cdm/src/main/java/ucar/nc2/time/CalendarDate.java

@@ -18,6 +18,13 @@
 @Immutable
 public class CalendarDate implements Comparable<CalendarDate> {
 
+  public static final double MILLISECS_IN_SECOND = 1000;
+  public static final double MILLISECS_IN_MINUTE = MILLISECS_IN_SECOND * 60;
+  public static final double MILLISECS_IN_HOUR = MILLISECS_IN_MINUTE * 60;
+  public static final double MILLISECS_IN_DAY = MILLISECS_IN_HOUR * 24;
+  public static final double MILLISECS_IN_YEAR = 3.15569259747E10;
+  public static final double MILLISECS_IN_MONTH = MILLISECS_IN_YEAR / 12;
+
   /**
    * Get a CalendarDate representing the present moment
    * @return CalendarDate representing the present moment in UTC
@@ -228,27 +235,22 @@ public int getHourOfDay() {
   }
 
   // old style udunits compatible.
-  /* day = 86400.0 seconds
-    week = 7 days = 604800.0 seconds
-    month = year/12 = 2629743.831225 seconds
-    year = 3.15569259747E7 seconds
-    */
   public CalendarDate add(double value, CalendarPeriod.Field unit) {
     switch (unit) {
       case Millisec:
-        return new CalendarDate(cal, dateTime.plus( (long) value ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value) ));
       case Second:
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 1000) ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_SECOND) ));
       case Minute:
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 60  * 1000) ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_MINUTE) ));
       case Hour:
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 60 * 60  * 1000) ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_HOUR) ));
       case Day:
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 86400  * 1000) ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_DAY) ));
       case Month: // LOOK should we throw warning ?
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 2629743.831225  * 1000) ));
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_MONTH) ));
       case Year:  // LOOK should we throw warning ?
-        return new CalendarDate(cal, dateTime.plus( (long) (value * 3.15569259747E10) )); // millisecs!
+        return new CalendarDate(cal, dateTime.plus( Math.round(value * MILLISECS_IN_YEAR) )); 
     }
     throw new UnsupportedOperationException("period units = "+unit);
   }

cdm/src/test/java/ucar/nc2/time/TestCalendarDate.java

@@ -1,7 +1,11 @@
 package ucar.nc2.time;
 
+import static org.junit.Assert.assertEquals;
+
 import org.junit.Test;
 
+import ucar.nc2.time.CalendarPeriod.Field;
+
 /**
  * CalendarDate testing
  *
@@ -36,4 +40,25 @@ public void testDateTimeFields() {
     cd = CalendarDate.of(null, 1,1,1,1,1,0);
   }
 
+  @Test
+  public void testAddReturnsClosestDate() {
+    String baseDate = "1950-01-01";
+    double valueInMillisecs = 2025829799999.99977;
+    String expectedResult = "2014-03-13T02:30:00Z";
+
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs, Field.Millisec, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_SECOND, Field.Second, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_MINUTE, Field.Minute, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_HOUR, Field.Hour, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_DAY, Field.Day, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_MONTH, Field.Month, expectedResult);
+    assertAddReturnsExpectedDate(baseDate, valueInMillisecs/CalendarDate.MILLISECS_IN_YEAR, Field.Year, expectedResult);
+  }
+
+  private void assertAddReturnsExpectedDate(String baseDate, double value, Field units, String expectedResult) {
+    CalendarDate base = CalendarDateFormatter.isoStringToCalendarDate(Calendar.gregorian, baseDate);
+    CalendarDate result = base.add(value, units);
+    assertEquals(units.toString(), expectedResult, CalendarDateFormatter.toDateTimeStringISO(result));
+  }
+
 }