Dan Moore!

SimpleDateFormat and the 13th month

Wow. I just learned something about SimpleDateFormat, a class that I always resort to when I have to convert a String to a Date in java. Check out this bit of code:

import java.text.*;
import java.util.*;

public class foo {
public static void main (String[] args) throws Exception {
SimpleDateFormat sdf = new SimpleDateFormat("MMddyyyy");
System.out.println("12012000 "+ sdf.parse("12012000"));
System.out.println("13012000 "+ sdf.parse("13012000"));
System.out.println("12322000 "+ sdf.parse("12322000"));
}
}


and the output from that code:

$ java -classpath . foo
12012000 Fri Dec 01 00:00:00 MST 2000
13012000 Mon Jan 01 00:00:00 MST 2001
12322000 Mon Jan 01 00:00:00 MST 2001


Any overflow gets rolled into the the next higher, well, in addition, I'd call this a place. The 32nd day of December is the 1st of Jan, and the 13th month of any year is Jan. This is an implementation detail, as I found no mention of it in the SimpleDateFormat javadoc, nor the DateFormat javadoc, but others have noticed this too.