Convert SAS date value to Java YYYY-MM-DD

Question

I have SAS date objects stored as integer and they look like : 19725. I am trying to write java code to convert the date to YYYY-MM-DD I see in the documentation that the SAS date value is the number of days from 01 Jan 1960 For example:

02 Jan 1960 would return 1 04 June 2003 would return 15680

Could you give the java code for this conversion. ie. convert something like 19725 to the date format : YYYY-MM-DD

I try the logic below but 15680 gives 2003-01-06 and not 2003-06-04 as the output. Could anyone point the mistake.Thanks in advance.

int numdays = 15680;    
Calendar cal = Calendar.getInstance();    
    cal.set(Calendar.DAY_OF_MONTH, 1);
    cal.set(Calendar.MONTH, 1);
    cal.set(Calendar.YEAR, 1960);
    cal.add(Calendar.DAY_OF_MONTH, numdays);

    String strdate = null;

    SimpleDateFormat sdf = new SimpleDateFormat("YYYY-MM-DD");

    if (cal != null) {
    strdate = sdf.format(cal.getTime());
    }
    System.out.println(strdate);

Answer 1

Month are 0-based, so you're setting your calendar to February, not January. This should fix the issue:

Calendar cal = Calendar.getInstance();    
cal.set(Calendar.DAY_OF_MONTH, 1);
cal.set(Calendar.MONTH, Calendar.JANUARY);
// ...

Answer 2

In addition to RC's point about starting the month correctly with Calendar.JANUARY, your simpledateformat is wrong.

SimpleDateFormat sdf = new SimpleDateFormat("YYYY-MM-dd");

'DD' is day of year (so 340th day of the year is Dec 6). 'dd' is day of the month. See the doc for more detail. (Also note that 15680 is Dec 6 2002, not what you say in the question.)

You may actually want to use 'yy' also:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");

as 'YYYY' is "Week Year", which in some cases may differ from yyyy (calendar year) near the end of the year. See the docs for more details.

Answer 3

I like to use JodaTime for date manipulation like this.

http://www.joda.org/joda-time/apidocs/org/joda/time/DateTime.html#plusDays-int-

int sasDate = 19725;
DateTime base = new DateTime(1960, 1, 1, 0, 0);
DateTime computed = base.plusDays(sasDate);