Index: src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java
===================================================================
RCS file: /home/cvspublic/jakarta-poi/src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java,v
retrieving revision 1.7
diff -u -r1.7 HSSFDateUtil.java
--- src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java 1 Jan 2004 09:03:32 -0000 1.7
+++ src/java/org/apache/poi/hssf/usermodel/HSSFDateUtil.java 10 Mar 2004 16:43:44 -0000
@@ -70,6 +70,7 @@
* @author Michael Harhen
* @author Glen Stampoultzis (glens at apache.org)
* @author Dan Sherman (dsherman at isisph.com)
+ * @author Hack Kampbjorn (hak at 2mba.dk)
*/
public class HSSFDateUtil
@@ -105,9 +106,19 @@
}
else
{
+ // Because of daylight time saving we cannot use
+ // date.getTime() - calStart.getTimeInMillis()
+ // as the difference in milliseconds between 00:00 and 04:00
+ // can be 3, 4 or 5 hours but Excel expects it to always
+ // be 4 hours.
+ // E.g. 2004-03-28 04:00 CEST - 2004-03-28 00:00 CET is 3 hours
+ // and 2004-10-31 04:00 CET - 2004-10-31 00:00 CEST is 5 hours
+ double fraction = (((calStart.get(Calendar.HOUR_OF_DAY) * 60
+ + calStart.get(Calendar.MINUTE)
+ ) * 60 + calStart.get(Calendar.SECOND)
+ ) * 1000 + calStart.get(Calendar.MILLISECOND)
+ ) / ( double ) DAY_MILLISECONDS;
calStart = dayStart(calStart);
- double fraction = (date.getTime() - calStart.getTime().getTime())
- / ( double ) DAY_MILLISECONDS;
return fraction + ( double ) absoluteDay(calStart)
- CAL_1900_ABSOLUTE;
@@ -133,10 +144,20 @@
* Given an Excel date with either 1900 or 1904 date windowing,
* converts it to a java.util.Date.
*
+ * NOTE: If the default TimeZone in Java uses Daylight
+ * Saving Time then the conversion back to an Excel date may not give
+ * the same value, that is the comparison
+ * excelDate == getExcelDate(getJavaDate(excelDate,false))
+ * is not always true. For example if default timezone is
+ * Europe/Copenhagen, on 2004-03-28 the minute after
+ * 01:59 CET is 03:00 CEST, if the excel date represents a time between
+ * 02:00 and 03:00 then it is converted to past 03:00 summer time
+ *
* @param date The Excel date.
* @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
+ * @see java.util.TimeZone
*/
public static Date getJavaDate(double date, boolean use1904windowing) {
if (isValidExcelDate(date)) {
Index: src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java
===================================================================
RCS file: /home/cvspublic/jakarta-poi/src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java,v
retrieving revision 1.3
diff -u -r1.3 TestHSSFDateUtil.java
--- src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java 30 Apr 2003 04:38:58 -0000 1.3
+++ src/testcases/org/apache/poi/hssf/usermodel/TestHSSFDateUtil.java 10 Mar 2004 16:43:46 -0000
@@ -58,7 +58,9 @@
import junit.framework.TestCase;
import java.util.Date;
+import java.util.Calendar;
import java.util.GregorianCalendar;
+import java.util.TimeZone;
/**
* Class TestHSSFDateUtil
@@ -66,6 +68,7 @@
*
* @author
* @author Dan Sherman (dsherman at isisph.com)
+ * @author Hack Kampbjorn (hak at 2mba.dk)
* @version %I%, %G%
*/
@@ -115,4 +118,111 @@
dateIf1904.getTime(),
HSSFDateUtil.getJavaDate(excelDate,true).getTime());
}
+
+ /**
+ * Checks the conversion of a java.util.date to Excel on a day when
+ * Daylight Saving Time starts.
+ */
+ public void testExcelConversionOnDSTStart() {
+ TimeZone cet = TimeZone.getTimeZone("Europe/Copenhagen");
+ TimeZone.setDefault(cet);
+ Calendar cal = new GregorianCalendar(2004, Calendar.MARCH, 28);
+ for (int hour = 0; hour < 24; hour++) {
+
+ // Skip 02:00 CET as that is the Daylight change time
+ // and Java converts it automatically to 03:00 CEST
+ if (hour == 2) {
+ continue;
+ }
+
+ cal.set(Calendar.HOUR_OF_DAY, hour);
+ Date javaDate = cal.getTime();
+ double excelDate = HSSFDateUtil.getExcelDate(javaDate);
+ double difference = excelDate - Math.floor(excelDate);
+ int differenceInHours = (int) (difference * 24 * 60 + 0.5) / 60;
+ assertEquals("Checking " + hour + " hour on Daylight Saving Time start date",
+ hour,
+ differenceInHours);
+ assertEquals("Checking " + hour + " hour on Daylight Saving Time start date",
+ javaDate.getTime(),
+ HSSFDateUtil.getJavaDate(excelDate).getTime());
+ }
+ }
+
+ /**
+ * Checks the conversion of an Excel date to a java.util.date on a day when
+ * Daylight Saving Time starts.
+ */
+ public void testJavaConversionOnDSTStart() {
+ TimeZone cet = TimeZone.getTimeZone("Europe/Copenhagen");
+ TimeZone.setDefault(cet);
+ Calendar cal = new GregorianCalendar(2004, Calendar.MARCH, 28);
+ double excelDate = HSSFDateUtil.getExcelDate(cal.getTime());
+ double oneHour = 1.0 / 24;
+ double oneMinute = oneHour / 60;
+ for (int hour = 0; hour < 24; hour++, excelDate += oneHour) {
+
+ // Skip 02:00 CET as that is the Daylight change time
+ // and Java converts it automatically to 03:00 CEST
+ if (hour == 2) {
+ continue;
+ }
+
+ cal.set(Calendar.HOUR_OF_DAY, hour);
+ Date javaDate = HSSFDateUtil.getJavaDate(excelDate);
+ assertEquals("Checking " + hour + " hours on Daylight Saving Time start date",
+ excelDate,
+ HSSFDateUtil.getExcelDate(javaDate), oneMinute);
+ }
+ }
+
+ /**
+ * Checks the conversion of a java.util.Date to Excel on a day when
+ * Daylight Saving Time ends.
+ */
+ public void testExcelConversionOnDSTEnd() {
+ TimeZone cet = TimeZone.getTimeZone("Europe/Copenhagen");
+ TimeZone.setDefault(cet);
+ Calendar cal = new GregorianCalendar(2004, Calendar.OCTOBER, 31);
+ for (int hour = 0; hour < 24; hour++) {
+ cal.set(Calendar.HOUR_OF_DAY, hour);
+ Date javaDate = cal.getTime();
+ double excelDate = HSSFDateUtil.getExcelDate(javaDate);
+ double difference = excelDate - Math.floor(excelDate);
+ int differenceInHours = (int) (difference * 24 * 60 + 0.5) / 60;
+ assertEquals("Checking " + hour + " hour on Daylight Saving Time end date",
+ hour,
+ differenceInHours);
+ assertEquals("Checking " + hour + " hour on Daylight Saving Time start date",
+ javaDate.getTime(),
+ HSSFDateUtil.getJavaDate(excelDate).getTime());
+ }
+ }
+
+ /**
+ * Checks the conversion of an Excel date to java.util.Date on a day when
+ * Daylight Saving Time ends.
+ */
+ public void testJavaConversionOnDSTEnd() {
+ TimeZone cet = TimeZone.getTimeZone("Europe/Copenhagen");
+ TimeZone.setDefault(cet);
+ Calendar cal = new GregorianCalendar(2004, Calendar.OCTOBER, 31);
+ double excelDate = HSSFDateUtil.getExcelDate(cal.getTime());
+ double oneHour = 1.0 / 24;
+ double oneMinute = oneHour / 60;
+ for (int hour = 0; hour < 24; hour++, excelDate += oneHour) {
+ cal.set(Calendar.HOUR_OF_DAY, hour);
+ Date javaDate = HSSFDateUtil.getJavaDate(excelDate);
+ assertEquals("Checking " + hour + " hours on Daylight Saving Time start date",
+ excelDate,
+ HSSFDateUtil.getExcelDate(javaDate), oneMinute);
+ }
+ }
+
+ public static void main(String [] args) {
+ System.out
+ .println("Testing org.apache.poi.hssf.usermodel.TestHSSFDateUtil");
+ junit.textui.TestRunner.run(TestHSSFDateUtil.class);
+ }
+
}