Fix bug #53092 - allow specifying of a TimeZone to DateUtil.getJavaDate(), for when it is known that a file comes from a different (known) timezone to the current machine

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1331477 13f79535-47bb-0310-9956-ffa450edef68

src/documentation/content/xdocs/status.xml

@@ -34,6 +34,7 @@
 
     <changes>
         <release version="3.9-beta1" date="2012-??-??">
+          <action dev="poi-developers" type="fix">53092 - allow specifying of a TimeZone to DateUtil.getJavaDate(), for when it is known that a file comes from a different (known) timezone to the current machine</action>
           <action dev="poi-developers" type="fix">53043 - don't duplicate hyperlink relationships when saving XSSF file</action>
           <action dev="poi-developers" type="fix">53101 - fixed evaluation of SUM over cell range &gt; 255</action>
           <action dev="poi-developers" type="fix">49529 - avoid exception when cloning sheets with no drawing records and initialized drawing patriarch</action>

src/java/org/apache/poi/ss/usermodel/DateUtil.java

@@ -21,6 +21,7 @@ package org.apache.poi.ss.usermodel;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
+import java.util.TimeZone;
 import java.util.regex.Pattern;
 
 /**
@@ -124,6 +125,22 @@ public class DateUtil {
         return value;
     }
 
+    /**
+     *  Given an Excel date with using 1900 date windowing, and
+     *  converts it to a java.util.Date.
+     *  
+     *  Excel Dates and Times are stored without any timezone 
+     *  information. If you know (through other means) that your file 
+     *  uses a different TimeZone to the system default, you can use
+     *  this version of the getJavaDate() method to handle it.
+     *   
+     *  @param date  The Excel date.
+     *  @param tz The TimeZone to evaluate the date in
+     *  @return Java representation of the date, or null if date is not a valid Excel date
+     */
+    public static Date getJavaDate(double date, TimeZone tz) {
+       return getJavaDate(date, false, tz);
+    }
     /**
      *  Given an Excel date with using 1900 date windowing, and
      *   converts it to a java.util.Date.
@@ -142,7 +159,38 @@ public class DateUtil {
      *  @see java.util.TimeZone
      */
     public static Date getJavaDate(double date) {
-        return getJavaDate(date, false);
+        return getJavaDate(date, (TimeZone)null);
+    }
+    
+    /**
+     *  Given an Excel date with either 1900 or 1904 date windowing,
+     *  converts it to a java.util.Date.
+     *  
+     *  Excel Dates and Times are stored without any timezone 
+     *  information. If you know (through other means) that your file 
+     *  uses a different TimeZone to the system default, you can use
+     *  this version of the getJavaDate() method to handle it.
+     *   
+     *  @param date  The Excel date.
+     *  @param tz The TimeZone to evaluate the date in
+     *  @param use1904windowing  true if date uses 1904 windowing,
+     *   or false if using 1900 date windowing.
+     *  @return Java representation of the date, or null if date is not a valid Excel date
+     */
+    public static Date getJavaDate(double date, boolean use1904windowing, TimeZone tz) {
+       if (!isValidExcelDate(date)) {
+          return null;
+       }
+       Calendar calendar;
+       if (tz != null)
+          calendar = new GregorianCalendar(tz);
+       else
+          calendar = new GregorianCalendar(); // using default time-zone
+       
+      int wholeDays = (int)Math.floor(date);
+      int millisecondsInDay = (int)((date - wholeDays) * DAY_MILLISECONDS + 0.5);
+      setCalendar(calendar, wholeDays, millisecondsInDay, use1904windowing);
+      return calendar.getTime();
     }
     /**
      *  Given an Excel date with either 1900 or 1904 date windowing,
@@ -164,14 +212,7 @@ public class DateUtil {
      *  @see java.util.TimeZone
      */
     public static Date getJavaDate(double date, boolean use1904windowing) {
-        if (!isValidExcelDate(date)) {
-            return null;
-        }
-        int wholeDays = (int)Math.floor(date);
-        int millisecondsInDay = (int)((date - wholeDays) * DAY_MILLISECONDS + 0.5);
-        Calendar calendar = new GregorianCalendar(); // using default time-zone
-        setCalendar(calendar, wholeDays, millisecondsInDay, use1904windowing);
-        return calendar.getTime();
+       return getJavaDate(date, use1904windowing, (TimeZone)null);
     }
     public static void setCalendar(Calendar calendar, int wholeDays,
             int millisecondsInDay, boolean use1904windowing) {

src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java

@@ -202,6 +202,25 @@ public final class TestHSSFDateUtil extends TestCase {
             // Should match despite time-zone
             assertEquals("Checking timezone " + id, expected.getTime(), javaDate.getTime());
         }
+        
+        // Check that the timezone aware getter works correctly 
+        TimeZone cet = TimeZone.getTimeZone("Europe/Copenhagen");
+        TimeZone ldn = TimeZone.getTimeZone("Europe/London");
+        TimeZone.setDefault(cet);
+        
+        // 12:45 on 27th April 2012
+        double excelDate = 41026.53125;
+        
+        // Same, no change
+        assertEquals(
+              HSSFDateUtil.getJavaDate(excelDate, false).getTime(),
+              HSSFDateUtil.getJavaDate(excelDate, false, cet).getTime()
+        );
+        
+        // London vs Copenhagen, should differ by an hour
+        Date cetDate = HSSFDateUtil.getJavaDate(excelDate, false);
+        Date ldnDate = HSSFDateUtil.getJavaDate(excelDate, false, ldn);
+        assertEquals(ldnDate.getTime() - cetDate.getTime(), 60*60*1000);
     }
 
     /**