Program in Java to convert a date to serial number as done in Excel

Question

I have written a function but it does not give an actual O/P...

public int date(Object O) {
    if (O instanceof Date) {
        Date d1 = (Date) O;
                 


        

Answer 1

Try this:

Date begin = new Date(0, 0, 1); // 1900 based date
Date date = new Date(108, 4, 18); // your date

// There is 2 days offset from the calculated date and what you 
// expect so I added it on the result
System.out.println(2+(date.getTime()-begin.getTime())/(1000*60*60*24));

See java.util.Date JavaDoc && Excel Date Function Guide

Answer 2

The problem in the program is :

In the program, variable mm(month) is coming as 4 and O/P is coming for 4th month only. (The first month of the year is 0)

To Solve this, you need to increase the month value.

    dd = cal.get(Calendar.DAY_OF_MONTH);
    mm = cal.get(Calendar.MONTH);
    yy = cal.get(Calendar.YEAR);

    //Solution for the issue
    mm++;

    if (dd == 29 && mm == 02 && yy == 1900)
        return 60;

    long nSerialDate = ((1461 * (yy + 4800 + ((mm - 14) / 12))) / 4)
            + ((367 * (mm - 2 - 12 * ((mm - 14) / 12))) / 12)
            - ((3 * (((yy + 4900 + ((mm - 14) / 12)) / 100))) / 4) + dd
            - 2415019 - 32075;

Answer 3

The right algorithm is already implemented in Apache POI. Take a look at class org.apache.poi.ss.usermodel.DateUtil.

Also this description could be useful: http://support.microsoft.com/kb/214094/en-us