Inspired by bug #44958 - Record level support for Data Tables. (No formula parser...

[poi.git] / src / java / org / apache / poi / hssf / usermodel / HSSFDateUtil.java

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   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
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/*
 * DateUtil.java
 *
 * Created on January 19, 2002, 9:30 AM
 */
package org.apache.poi.hssf.usermodel;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

/**
 * Contains methods for dealing with Excel dates.
 *
 * @author  Michael Harhen
 * @author  Glen Stampoultzis (glens at apache.org)
 * @author  Dan Sherman (dsherman at isisph.com)
 * @author  Hack Kampbjorn (hak at 2mba.dk)
 * @author  Alex Jacoby (ajacoby at gmail.com)
 * @author  Pavel Krupets (pkrupets at palmtreebusiness dot com)
 */

public class HSSFDateUtil
{
    private HSSFDateUtil()
    {
    }

    private static final int    BAD_DATE         =
        -1;   // used to specify that date is invalid
    private static final long   DAY_MILLISECONDS = 24 * 60 * 60 * 1000;
    
    /**
     * Given a Date, converts it into a double representing its internal Excel representation,
     *   which is the number of days since 1/1/1900. Fractional days represent hours, minutes, and seconds.
     *
     * @return Excel representation of Date (-1 if error - test for error by checking for less than 0.1)
     * @param  date the Date
     */
    public static double getExcelDate(Date date) {
        return getExcelDate(date, false);
    }
    /**
     * Given a Date, converts it into a double representing its internal Excel representation,
     *   which is the number of days since 1/1/1900. Fractional days represent hours, minutes, and seconds.
     *
     * @return Excel representation of Date (-1 if error - test for error by checking for less than 0.1)
     * @param date the Date
     * @param use1904windowing Should 1900 or 1904 date windowing be used?
     */
    public static double getExcelDate(Date date, boolean use1904windowing) {
        Calendar calStart = new GregorianCalendar();
        calStart.setTime(date);   // If date includes hours, minutes, and seconds, set them to 0
        return internalGetExcelDate(calStart, use1904windowing);
    }
    /**
     * Given a Date in the form of a Calendar, converts it into a double
     *  representing its internal Excel representation, which is the 
     *  number of days since 1/1/1900. Fractional days represent hours, 
     *  minutes, and seconds.
     *
     * @return Excel representation of Date (-1 if error - test for error by checking for less than 0.1)
     * @param date the Calendar holding the date to convert
     * @param use1904windowing Should 1900 or 1904 date windowing be used?
     */
    public static double getExcelDate(Calendar date, boolean use1904windowing) {
        // Don't alter the supplied Calendar as we do our work
        return internalGetExcelDate( (Calendar)date.clone(), use1904windowing );
    }
    private static double internalGetExcelDate(Calendar date, boolean use1904windowing) {
        if ((!use1904windowing && date.get(Calendar.YEAR) < 1900) || 
            (use1904windowing && date.get(Calendar.YEAR) < 1904)) 
        {
            return BAD_DATE;
        } 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 = (((date.get(Calendar.HOUR_OF_DAY) * 60
                                 + date.get(Calendar.MINUTE)
                                ) * 60 + date.get(Calendar.SECOND)
                               ) * 1000 + date.get(Calendar.MILLISECOND)
                              ) / ( double ) DAY_MILLISECONDS;
            Calendar calStart = dayStart(date);
            
            double value = fraction + absoluteDay(calStart, use1904windowing);
            
            if (!use1904windowing && value >= 60) {
                value++;
            } else if (use1904windowing) {
                value--;
            }
            
            return value;
        }
    }
    
    /**
     *  Given an Excel date with using 1900 date windowing, and
     *   converts it to a java.util.Date.
     *
     *  NOTE: If the default <code>TimeZone</code> in Java uses Daylight
     *  Saving Time then the conversion back to an Excel date may not give
     *  the same value, that is the comparison
     *  <CODE>excelDate == getExcelDate(getJavaDate(excelDate,false))</CODE>
     *  is not always true. For example if default timezone is
     *  <code>Europe/Copenhagen</code>, 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.
     *  @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) {
        return getJavaDate(date, false);
    }
    /**
     *  Given an Excel date with either 1900 or 1904 date windowing,
     *  converts it to a java.util.Date.
     *
     *  NOTE: If the default <code>TimeZone</code> in Java uses Daylight
     *  Saving Time then the conversion back to an Excel date may not give
     *  the same value, that is the comparison
     *  <CODE>excelDate == getExcelDate(getJavaDate(excelDate,false))</CODE>
     *  is not always true. For example if default timezone is
     *  <code>Europe/Copenhagen</code>, 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)) {
            int startYear = 1900;
            int dayAdjust = -1; // Excel thinks 2/29/1900 is a valid date, which it isn't
            int wholeDays = (int)Math.floor(date);
            if (use1904windowing) {
                startYear = 1904;
                dayAdjust = 1; // 1904 date windowing uses 1/2/1904 as the first day
            }
            else if (wholeDays < 61) {
                // Date is prior to 3/1/1900, so adjust because Excel thinks 2/29/1900 exists
                // If Excel date == 2/29/1900, will become 3/1/1900 in Java representation
                dayAdjust = 0;
            }
            GregorianCalendar calendar = new GregorianCalendar(startYear,0,
                                                     wholeDays + dayAdjust);
            int millisecondsInDay = (int)((date - Math.floor(date)) * 
                                          DAY_MILLISECONDS + 0.5);
            calendar.set(GregorianCalendar.MILLISECOND, millisecondsInDay);
            return calendar.getTime();
        }
        else {
            return null;
        }
    }
    
    /**
     * Given a format ID and its format String, will check to see if the
     *  format represents a date format or not.
     * Firstly, it will check to see if the format ID corresponds to an
     *  internal excel date format (eg most US date formats) 
     * If not, it will check to see if the format string only contains
     *  date formatting characters (ymd-/), which covers most
     *  non US date formats.
     *  
     * @param formatIndex The index of the format, eg from ExtendedFormatRecord.getFormatIndex
     * @param formatString The format string, eg from FormatRecord.getFormatString
     * @see #isInternalDateFormat(int)
     */
    public static boolean isADateFormat(int formatIndex, String formatString) {
        // First up, is this an internal date format?
        if(isInternalDateFormat(formatIndex)) {
                return true;
        }
        
        // If we didn't get a real string, it can't be
        if(formatString == null || formatString.length() == 0) {
                return false;
        }
        
        String fs = formatString;
        
        // Translate \- into just -, before matching
        fs = fs.replaceAll("\\\\-","-");
        // And \, into ,
        fs = fs.replaceAll("\\\\,",",");
        // And '\ ' into ' '
        fs = fs.replaceAll("\\\\ "," ");
        
        // If it end in ;@, that's some crazy dd/mm vs mm/dd
        //  switching stuff, which we can ignore
        fs = fs.replaceAll(";@", "");
        
        // If it starts with [$-...], then could be a date, but
        //  who knows what that starting bit is all about
        fs = fs.replaceAll("^\\[\\$\\-.*?\\]", "");
        
        // If it starts with something like [Black] or [Yellow],
        //  then it could be a date
        fs = fs.replaceAll("^\\[[a-zA-Z]+\\]", "");
        
        // Otherwise, check it's only made up, in any case, of:
        //  y m d h s - / , . :
        // optionally followed by AM/PM
        if(fs.matches("^[yYmMdDhHsS\\-/,. :]+[ampAMP]*$")) {
                return true;
        }
        
        return false;
    }

    /**
     * Given a format ID this will check whether the format represents
     *  an internal excel date format or not.
     * @see #isADateFormat(int, java.lang.String)  
     */
    public static boolean isInternalDateFormat(int format) {
      boolean retval =false;

            switch(format) {
                // Internal Date Formats as described on page 427 in
                // Microsoft Excel Dev's Kit...
                case 0x0e:
                case 0x0f:
                case 0x10:
                case 0x11:
                case 0x12:
                case 0x13:
                case 0x14:
                case 0x15:
                case 0x16:
                case 0x2d:
                case 0x2e:
                case 0x2f:
                    retval = true;
                    break;
                    
                default:
                    retval = false;
                    break;
            }
       return retval;
    }

    /**
     *  Check if a cell contains a date
     *  Since dates are stored internally in Excel as double values 
     *  we infer it is a date if it is formatted as such. 
     *  @see #isADateFormat(int, String)
     *  @see #isInternalDateFormat(int)
     */
    public static boolean isCellDateFormatted(HSSFCell cell) {
        if (cell == null) return false;
        boolean bDate = false;
        
        double d = cell.getNumericCellValue();
        if ( HSSFDateUtil.isValidExcelDate(d) ) {
            HSSFCellStyle style = cell.getCellStyle();
            int i = style.getDataFormat();
            String f = style.getDataFormatString(cell.getBoundWorkbook());
            bDate = isADateFormat(i, f);
        }
        return bDate;
    }
    /**
     *  Check if a cell contains a date, checking only for internal
     *   excel date formats.
     *  As Excel stores a great many of its dates in "non-internal"
     *   date formats, you will not normally want to use this method.
     *  @see #isADateFormat(int,String)
     *  @see #isInternalDateFormat(int)
     */
    public static boolean isCellInternalDateFormatted(HSSFCell cell) {
        if (cell == null) return false;
        boolean bDate = false;
        
        double d = cell.getNumericCellValue();
        if ( HSSFDateUtil.isValidExcelDate(d) ) {
            HSSFCellStyle style = cell.getCellStyle();
            int i = style.getDataFormat();
            bDate = isInternalDateFormat(i);
        }
        return bDate;
    }


    /**
     * Given a double, checks if it is a valid Excel date.
     *
     * @return true if valid
     * @param  value the double value
     */

    public static boolean isValidExcelDate(double value)
    {
        return (value > -Double.MIN_VALUE);
    }

    /**
     * Given a Calendar, return the number of days since 1900/12/31.
     *
     * @return days number of days since 1900/12/31
     * @param  cal the Calendar
     * @exception IllegalArgumentException if date is invalid
     */

    static int absoluteDay(Calendar cal, boolean use1904windowing)
    {
        return cal.get(Calendar.DAY_OF_YEAR)
               + daysInPriorYears(cal.get(Calendar.YEAR), use1904windowing);
    }

    /**
     * Return the number of days in prior years since 1900
     *
     * @return    days  number of days in years prior to yr.
     * @param     yr    a year (1900 < yr < 4000)
     * @param use1904windowing 
     * @exception IllegalArgumentException if year is outside of range.
     */

    private static int daysInPriorYears(int yr, boolean use1904windowing)
    {
        if ((!use1904windowing && yr < 1900) || (use1904windowing && yr < 1900)) {
            throw new IllegalArgumentException("'year' must be 1900 or greater");
        }
        
        int yr1  = yr - 1;
        int leapDays =   yr1 / 4   // plus julian leap days in prior years
                       - yr1 / 100 // minus prior century years
                       + yr1 / 400 // plus years divisible by 400 
                       - 460;      // leap days in previous 1900 years
        
        return 365 * (yr - (use1904windowing ? 1904 : 1900)) + leapDays;
    }
    
    // set HH:MM:SS fields of cal to 00:00:00:000
    private static Calendar dayStart(final Calendar cal)
    {
        cal.get(Calendar
            .HOUR_OF_DAY);   // force recalculation of internal fields
        cal.set(Calendar.HOUR_OF_DAY, 0);
        cal.set(Calendar.MINUTE, 0);
        cal.set(Calendar.SECOND, 0);
        cal.set(Calendar.MILLISECOND, 0);
        cal.get(Calendar
            .HOUR_OF_DAY);   // force recalculation of internal fields
        return cal;
    }

    // ---------------------------------------------------------------------------------------------------------
}