blocks|key|3184283|text|http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3184284|CellStyle+cellStyle+=+wb.createCellStyle();
CreationHelper+createHelper+=+wb.getCreationHelper();
cellStyle.setDataFormat(
++++createHelper.createDataFormat().getFormat("m/d/yy+h:mm"));
cell+=+row.createCell(1);
cell.setCellValue(new+Date());
cell.setCellStyle(cellStyle);|code-block|syntax|javascript|3184285|entityMap|0|LINK|mutability|MUTABLE|url^0|0|1U|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|F|7|T|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|4]]]]

<a href="http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells">http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells</a>

<pre><code>CellStyle cellStyle = wb.createCellStyle();
CreationHelper createHelper = wb.getCreationHelper();
cellStyle.setDataFormat(
 createHelper.createDataFormat().getFormat("m/d/yy h:mm"));
cell = row.createCell(1);
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle);
</code></pre>

blocks|key|2970630|text|此示例用于处理.xlsx文件类型。此示例来自用于创建.xslx电子表格的.jsp页面。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2970631|import+org.apache.poi.xssf.usermodel.*;+//import+needed

XSSFWorkbook++wb+=+new+XSSFWorkbook+();++//+Create+workbook
XSSFSheet+sheet+=+wb.createSheet();++++++//+Create+spreadsheet+in+workbook
XSSFRow+row+=+sheet.createRow(rowIndex);+//+Create+the+row+in+the+spreadsheet


//1.+Create+the+date+cell+style
XSSFCreationHelper+createHelper+=+wb.getCreationHelper();
XSSFCellStyle+cellStyle+++++++++=+wb.createCellStyle();
cellStyle.setDataFormat(
createHelper.createDataFormat().getFormat("MMMM+dd,+yyyy"));+

//2.+Apply+the+Date+cell+style+to+a+cell

//This+example+sets+the+first+cell+in+the+row+using+the+date+cell+style
cell+=+row.createCell(0);
cell.setCellValue(new+Date());
cell.setCellStyle(cellStyle);|code-block|syntax|javascript|2970632|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This example is for working with .xlsx file types. This example comes from a .jsp page used to create a .xslx spreadsheet.

<pre><code>import org.apache.poi.xssf.usermodel.*; //import needed

XSSFWorkbook wb = new XSSFWorkbook (); // Create workbook
XSSFSheet sheet = wb.createSheet(); // Create spreadsheet in workbook
XSSFRow row = sheet.createRow(rowIndex); // Create the row in the spreadsheet


//1. Create the date cell style
XSSFCreationHelper createHelper = wb.getCreationHelper();
XSSFCellStyle cellStyle = wb.createCellStyle();
cellStyle.setDataFormat(
createHelper.createDataFormat().getFormat("MMMM dd, yyyy")); 

//2. Apply the Date cell style to a cell

//This example sets the first cell in the row using the date cell style
cell = row.createCell(0);
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle);
</code></pre>

blocks|key|272396|text|此代码示例可用于更改日期格式。这里我想从yyyy-MM-dd更改为dd-MM-yyyy。这里pos是列的位置。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|272397|import+org.apache.poi.ss.usermodel.Cell;
import+org.apache.poi.ss.usermodel.CellStyle;
import+org.apache.poi.ss.usermodel.CreationHelper;
import+org.apache.poi.ss.usermodel.Row;
import+org.apache.poi.xssf.usermodel.XSSFCellStyle;
import+org.apache.poi.xssf.usermodel.XSSFColor;
import+org.apache.poi.xssf.usermodel.XSSFFont;
import+org.apache.poi.xssf.usermodel.XSSFSheet;
import+org.apache.poi.xssf.usermodel.XSSFWorkbook;

class+Test{+
public+static+void+main(+String[]+args+)
{
String+input="D:\\somefolder\\somefile.xlsx";
String+output="D:\\somefolder\\someoutfile.xlsx"
FileInputStream+file+=+new+FileInputStream(new+File(input));
XSSFWorkbook+workbook+=+new+XSSFWorkbook(file);
XSSFSheet+sheet+=+workbook.getSheetAt(0);
Iterator<Row>+iterator+=+sheet.iterator();
Cell+cell+=+null;
Row+row=null;
row=iterator.next();
int+pos=5;+//+5th+column+is+date.
while(iterator.hasNext())
{
++++row=iterator.next();

++++cell=row.getCell(pos-1);
++++//CellStyle+cellStyle+=+wb.createCellStyle();
++++XSSFCellStyle+cellStyle+=+(XSSFCellStyle)cell.getCellStyle();
++++CreationHelper+createHelper+=+wb.getCreationHelper();
++++cellStyle.setDataFormat(
++++++++createHelper.createDataFormat().getFormat("dd-MM-yyyy"));
++++SimpleDateFormat+sdf+=+new+SimpleDateFormat("yyyy-MM-dd");
++++Date+d=null;
++++try+{
++++++++d=+sdf.parse(cell.getStringCellValue());
++++}+catch+(ParseException+e)+{
++++++++//+TODO+Auto-generated+catch+block
++++++++d=null;
++++++++e.printStackTrace();
++++++++continue;
++++}
++++cell.setCellValue(d);
++++cell.setCellStyle(cellStyle);
+++}

file.close();
FileOutputStream+outFile+=new+FileOutputStream(new+File(output));
workbook.write(outFile);
workbook.close();
outFile.close();
}}|code-block|syntax|javascript|272398|entityMap^0|1A|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

This code sample can be used to change date format. Here I want to change from yyyy-MM-dd to dd-MM-yyyy. Here <code>pos</code> is position of column.

<pre><code>import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.CellStyle;
import org.apache.poi.ss.usermodel.CreationHelper;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.xssf.usermodel.XSSFCellStyle;
import org.apache.poi.xssf.usermodel.XSSFColor;
import org.apache.poi.xssf.usermodel.XSSFFont;
import org.apache.poi.xssf.usermodel.XSSFSheet;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

class Test{ 
public static void main( String[] args )
{
String input="D:\\somefolder\\somefile.xlsx";
String output="D:\\somefolder\\someoutfile.xlsx"
FileInputStream file = new FileInputStream(new File(input));
XSSFWorkbook workbook = new XSSFWorkbook(file);
XSSFSheet sheet = workbook.getSheetAt(0);
Iterator&lt;Row&gt; iterator = sheet.iterator();
Cell cell = null;
Row row=null;
row=iterator.next();
int pos=5; // 5th column is date.
while(iterator.hasNext())
{
 row=iterator.next();

 cell=row.getCell(pos-1);
 //CellStyle cellStyle = wb.createCellStyle();
 XSSFCellStyle cellStyle = (XSSFCellStyle)cell.getCellStyle();
 CreationHelper createHelper = wb.getCreationHelper();
 cellStyle.setDataFormat(
 createHelper.createDataFormat().getFormat("dd-MM-yyyy"));
 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
 Date d=null;
 try {
 d= sdf.parse(cell.getStringCellValue());
 } catch (ParseException e) {
 // TODO Auto-generated catch block
 d=null;
 e.printStackTrace();
 continue;
 }
 cell.setCellValue(d);
 cell.setCellStyle(cellStyle);
 }

file.close();
FileOutputStream outFile =new FileOutputStream(new File(output));
workbook.write(outFile);
workbook.close();
outFile.close();
}}
</code></pre>

blocks|key|2970723|text|要设置为默认的Excel类型日期(默认为操作系统级别的区域设置/->，即xlsx在由德国人或英国人打开时看起来不同，并且如果在Excel的单元格格式选择器中选择它，则会用星号标记)，您应该：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2970724|++++CellStyle+cellStyle+=+xssfWorkbook.createCellStyle();
++++cellStyle.setDataFormat((short)14);
++++cell.setCellStyle(cellStyle);|code-block|syntax|javascript|2970725|我用xlsx做了这件事，它工作得很好。|2970726|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

To set to default Excel type Date (defaulted to OS level locale /-> i.e. xlsx will look different when opened by a German or British person/ and flagged with an asterisk if you choose it in Excel's cell format chooser) you should:

<pre><code> CellStyle cellStyle = xssfWorkbook.createCellStyle();
 cellStyle.setDataFormat((short)14);
 cell.setCellStyle(cellStyle);
</code></pre>

I did it with xlsx and it worked fine.

blocks|key|268772|text|我在这里写下我的答案，因为它可能会对其他读者有所帮助，他们的要求可能与这里的提问者略有不同。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|268773|我准备了一个.xlsx模板；所有用日期填充的单元格都已经格式化为日期单元格(使用Excel)。|268774|我使用Apache+POI打开.xlsx模板，然后将日期写入单元格，它就可以工作了。|268775|在下面的示例中，单元格A1已经在Excel中以[$-409]mmm+yyyy格式进行了格式化，并且Java代码仅用于填充单元格。|offset|length|style|CODE|268776|FileInputStream+inputStream+=+new+FileInputStream(new+File("Path+to+.xlsx+template"));
Workbook+wb+=+new+XSSFWorkbook(inputStream);
Date+date1=new+Date();
Sheet+xlsMainTable+=+(Sheet)+wb.getSheetAt(0);
Row+myRow=+CellUtil.getRow(0,+xlsMainTable);
CellUtil.getCell(myRow,+0).setCellValue(date1);|code-block|syntax|javascript|268777|WHen打开Excel，日期格式正确。|268778|entityMap^0|0|0|0|N|F|0|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|V|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|X|8|@$H|Y|I|Z|J|K]]|9|@]|A|$]]|$1|L|3|M|5|N|7|10|8|@]|9|@]|A|$O|P]]|$1|Q|3|R|5|6|7|11|8|@]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

I am writing my answer here because it may be helpful to other readers, who might have a slightly different requirement than the questioner here.

I prepare an .xlsx template; all the cells which will be populated with dates, are already formatted as date cells (using Excel).

I open the .xlsx template using Apache POI and then just write the date to the cell, and it works.

In the example below, cell A1 is already formatted from within Excel with the format <code>[$-409]mmm yyyy</code>, and the Java code is used only to populate the cell.

<pre><code>FileInputStream inputStream = new FileInputStream(new File("Path to .xlsx template"));
Workbook wb = new XSSFWorkbook(inputStream);
Date date1=new Date();
Sheet xlsMainTable = (Sheet) wb.getSheetAt(0);
Row myRow= CellUtil.getRow(0, xlsMainTable);
CellUtil.getCell(myRow, 0).setCellValue(date1);
</code></pre>

WHen the Excel is opened, the date is formatted correctly.

blocks|key|270801|text|要知道Excel使用的格式字符串而无需猜测:创建一个excel文件，在单元格A1中写入日期，并根据需要设置其格式。然后运行以下代码行：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|270802|FileInputStream+fileIn+=+new+FileInputStream("test.xlsx");
Workbook+workbook+=+WorkbookFactory.create(fileIn);
CellStyle+cellStyle+=+workbook.getSheetAt(0).getRow(0).getCell(0).getCellStyle();
String+styleString+=+cellStyle.getDataFormatString();
System.out.println(styleString);|code-block|syntax|javascript|270803|然后复制粘贴生成的字符串，删除反斜杠(例如d/m/yy\+h\.mm;@变为d/m/yy+h.mm;@)，并在http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells代码中使用它：|offset|length|style|CODE|270804|CellStyle+cellStyle+=+wb.createCellStyle();
CreationHelper+createHelper+=+wb.getCreationHelper();
cellStyle.setDataFormat(createHelper.createDataFormat().getFormat("d/m/yy+h.mm;@"));
cell+=+row.createCell(1);
cell.setCellValue(new+Date());
cell.setCellStyle(cellStyle);|270805|entityMap|0|LINK|mutability|MUTABLE|url|http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells^0|0|0|L|F|12|D|1J|1U|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Y|8|@$I|Z|J|10|K|L]|$I|11|J|12|K|L]]|9|@$I|13|J|14|1|15]]|A|$]]|$1|M|3|N|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|17|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

To know the format string used by Excel without having to guess it: create an excel file, write a date in cell A1 and format it as you want. Then run the following lines:

<pre><code>FileInputStream fileIn = new FileInputStream("test.xlsx");
Workbook workbook = WorkbookFactory.create(fileIn);
CellStyle cellStyle = workbook.getSheetAt(0).getRow(0).getCell(0).getCellStyle();
String styleString = cellStyle.getDataFormatString();
System.out.println(styleString);
</code></pre>

Then copy-paste the resulting string, remove the backslashes (for example <code>d/m/yy\ h\.mm;@</code> becomes <code>d/m/yy h.mm;@</code>) and use it in the <a href="http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells" rel="nofollow noreferrer">http://poi.apache.org/spreadsheet/quick-guide.html#CreateDateCells</a> code:

<pre><code>CellStyle cellStyle = wb.createCellStyle();
CreationHelper createHelper = wb.getCreationHelper();
cellStyle.setDataFormat(createHelper.createDataFormat().getFormat("d/m/yy h.mm;@"));
cell = row.createCell(1);
cell.setCellValue(new Date());
cell.setCellStyle(cellStyle);
</code></pre>

blocks|key|270811|text|除了@BlondeCode+answer之外，以下是您可以使用creationHelper.createDataFormat().getFormat((short)+index)获得的所有可用格式的列表|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|270812|0=“常规”|270813|1=+"0“|270814|2=+"0.00“|270815|3=+"#，##0“|270816|4=+"#，##0.00“|270817|5=+""$"#，##0_);("$"#，##0)“|270818|6=+""$"#，##0_)；红色“|270819|7=+""$"#，##0.00_);("$"#，##0.00)“|270820|8=+""$"#，##0.00_)；红色“|270821|9=+"0%25“|270822|10+=+"0.00%25“|270823|11+=+"0.00E%2B00“|270824|12+=+"#+?/?“|270825|13+=+"#+??/??“|270826|14+=“年/月/日”|270827|15+=+"d-mmm-yy“|270828|16+=+"d-mmm“|270829|17+=“mmm+yy”|270830|18+=+"h:mm+AM/PM“|270831|19+=+"h:mm:ss+AM/PM“|270832|20+=+"h:mm“|270833|21+=+"h:mm:ss“|270834|22+=+"m/d/yy+h:mm“|270835|23-36+=保留|270836|37+=+"#，##0_);(#，##0)“|270837|38+=+"#，##0_)；红色“|270838|39+=+"#，##0.00_);(#，##0.00)“|270839|40+=+"#，##0.00_)；红色“|270840|41+=+"(*+#，##0);(*+(#，##0);(*+"-");(@)“|270841|42+=+"("$"*+#，##0_);("$"*+(#，##0);("$"*+"-");(@)“|270842|43+=+"(*+#，##0.00_);(*+(#，##0.00);(*+"-"??);(@)“|270843|44+=+"("$"*+#，##0.00_);("$"*+(#，##0.00);("$"*+"-"??);(@_)“|270844|45+=+"mm:ss“|270845|46+=+"h:mm:ss“|270846|47+=+"mm:ss.0“|270847|48+=+"##0.0E%2B0“|270848|49+=+"@“|270849|在索引164中，有您的自定义图案|270850|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/5794659/how-do-i-set-cell-value-to-date-and-apply-default-excel-date-format/41124537#41124537^0|V|1M|E|6|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|2R|8|@$9|2S|A|2T|B|C]]|D|@$9|2U|A|2V|1|2W]]|E|$]]|$1|F|3|G|5|6|7|2X|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|2Y|8|@]|D|@]|E|$]]|$1|J|3|K|5|6|7|2Z|8|@]|D|@]|E|$]]|$1|L|3|M|5|6|7|30|8|@]|D|@]|E|$]]|$1|N|3|O|5|6|7|31|8|@]|D|@]|E|$]]|$1|P|3|Q|5|6|7|32|8|@]|D|@]|E|$]]|$1|R|3|S|5|6|7|33|8|@]|D|@]|E|$]]|$1|T|3|U|5|6|7|34|8|@]|D|@]|E|$]]|$1|V|3|W|5|6|7|35|8|@]|D|@]|E|$]]|$1|X|3|Y|5|6|7|36|8|@]|D|@]|E|$]]|$1|Z|3|10|5|6|7|37|8|@]|D|@]|E|$]]|$1|11|3|12|5|6|7|38|8|@]|D|@]|E|$]]|$1|13|3|14|5|6|7|39|8|@]|D|@]|E|$]]|$1|15|3|16|5|6|7|3A|8|@]|D|@]|E|$]]|$1|17|3|18|5|6|7|3B|8|@]|D|@]|E|$]]|$1|19|3|1A|5|6|7|3C|8|@]|D|@]|E|$]]|$1|1B|3|1C|5|6|7|3D|8|@]|D|@]|E|$]]|$1|1D|3|1E|5|6|7|3E|8|@]|D|@]|E|$]]|$1|1F|3|1G|5|6|7|3F|8|@]|D|@]|E|$]]|$1|1H|3|1I|5|6|7|3G|8|@]|D|@]|E|$]]|$1|1J|3|1K|5|6|7|3H|8|@]|D|@]|E|$]]|$1|1L|3|1M|5|6|7|3I|8|@]|D|@]|E|$]]|$1|1N|3|1O|5|6|7|3J|8|@]|D|@]|E|$]]|$1|1P|3|1Q|5|6|7|3K|8|@]|D|@]|E|$]]|$1|1R|3|1S|5|6|7|3L|8|@]|D|@]|E|$]]|$1|1T|3|1U|5|6|7|3M|8|@]|D|@]|E|$]]|$1|1V|3|1W|5|6|7|3N|8|@]|D|@]|E|$]]|$1|1X|3|1Y|5|6|7|3O|8|@]|D|@]|E|$]]|$1|1Z|3|20|5|6|7|3P|8|@]|D|@]|E|$]]|$1|21|3|22|5|6|7|3Q|8|@]|D|@]|E|$]]|$1|23|3|24|5|6|7|3R|8|@]|D|@]|E|$]]|$1|25|3|26|5|6|7|3S|8|@]|D|@]|E|$]]|$1|27|3|28|5|6|7|3T|8|@]|D|@]|E|$]]|$1|29|3|2A|5|6|7|3U|8|@]|D|@]|E|$]]|$1|2B|3|2C|5|6|7|3V|8|@]|D|@]|E|$]]|$1|2D|3|2E|5|6|7|3W|8|@]|D|@]|E|$]]|$1|2F|3|2G|5|6|7|3X|8|@]|D|@]|E|$]]|$1|2H|3|2I|5|6|7|3Y|8|@]|D|@]|E|$]]|$1|2J|3|-4|5|6|7|3Z|8|@]|D|@]|E|$]]]|2K|$2L|$5|2M|2N|2O|E|$2P|2Q]]]]

In addition to @BlondeCode <a href="https://stackoverflow.com/questions/5794659/how-do-i-set-cell-value-to-date-and-apply-default-excel-date-format/41124537#41124537">answer</a>, here are the list of all available formats that you can get with
<code>creationHelper.createDataFormat().getFormat((short) index)</code>
0 = &quot;General&quot; 
1 = &quot;0&quot; 
2 = &quot;0.00&quot; 
3 = &quot;#,##0&quot; 
4 = &quot;#,##0.00&quot; 
5 = &quot;&quot;$&quot;#,##0_);(&quot;$&quot;#,##0)&quot; 
6 = &quot;&quot;$&quot;#,##0_);Red&quot; 
7 = &quot;&quot;$&quot;#,##0.00_);(&quot;$&quot;#,##0.00)&quot; 
8 = &quot;&quot;$&quot;#,##0.00_);Red&quot; 
9 = &quot;0%&quot; 
10 = &quot;0.00%&quot; 
11 = &quot;0.00E+00&quot; 
12 = &quot;# ?/?&quot; 
13 = &quot;# ??/??&quot; 
14 = &quot;m/d/yy&quot; 
15 = &quot;d-mmm-yy&quot; 
16 = &quot;d-mmm&quot; 
17 = &quot;mmm-yy&quot; 
18 = &quot;h:mm AM/PM&quot; 
19 = &quot;h:mm:ss AM/PM&quot; 
20 = &quot;h:mm&quot; 
21 = &quot;h:mm:ss&quot; 
22 = &quot;m/d/yy h:mm&quot; 
23-36 = reserved 
37 = &quot;#,##0_);(#,##0)&quot; 
38 = &quot;#,##0_);Red&quot; 
39 = &quot;#,##0.00_);(#,##0.00)&quot; 
40 = &quot;#,##0.00_);Red&quot; 
41 = &quot;(* #,##0);(* (#,##0);(* &quot;-&quot;);(@)&quot; 
42 = &quot;(&quot;$&quot;* #,##0_);(&quot;$&quot;* (#,##0);(&quot;$&quot;* &quot;-&quot;);(@)&quot; 
43 = &quot;(* #,##0.00_);(* (#,##0.00);(* &quot;-&quot;??);(@)&quot; 
44 = &quot;(&quot;$&quot;* #,##0.00_);(&quot;$&quot;* (#,##0.00);(&quot;$&quot;* &quot;-&quot;??);(@_)&quot; 
45 = &quot;mm:ss&quot; 
46 = &quot;[h]:mm:ss&quot; 
47 = &quot;mm:ss.0&quot; 
48 = &quot;##0.0E+0&quot; 
49 = &quot;@&quot; 
And from index 164, there are your custom patterns

I've been using Apache POI for some time to read existing Excel 2003 files programmatically. Now I have a new requirement to create entire .xls files in-memory (still using Apache POI) and then write them to a file at the end. The only problem standing in my way is the handling of cells with dates.

Consider the following code:

<pre><code>Date myDate = new Date();
HSSFCell myCell;
// code that assigns a cell from an HSSFSheet to 'myCell' would go here...
myCell.setCellValue(myDate);
</code></pre>

When I write the workbook containing this cell out to a file and open it with Excel, the cell is displayed as a number. Yes, I do realize that Excel stores its 'dates' as the number of days since January 1 1900 and that is what the number in the cell represents.

QUESTION: What API calls can I use in POI to tell it that I want a default date format applied to my date cell?

Ideally I want the spreadsheet cell to be displayed with the same default date format that Excel would have assigned it if a user had manually opened the spreadsheet in Excel and typed in a cell value that Excel recognized as being a date.

How do I set cell value to Date and apply default Excel date format?

Java

我使用Apache POI以编程方式读取现有的Excel2003文件已经有一段时间了。现在我有了一个新需求，需要在内存中创建整个.xls文件(仍然使用Apache POI)，然后在最后将它们写到一个文件中。我遇到的唯一问题是如何处理带日期的单元格。考虑以下代码：Date myDate = new Date();HSSF...

问如何将单元格值设置为日期并应用默认Excel日期格式？
EN

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问如何将单元格值设置为日期并应用默认Excel日期格式？
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