java - What's the difference between adding DAY_OF_MONTH or DAY_OF_YEAR to a Calendar object?

Question

I want to increase a certain date by 1 day. I create a Calendar object like:

Calendar cal = Calendar.getInstance();
cal.set(Calendar.YEAR, 2012);
cal.set(Calendar.MONTH, 0);
cal.set(Calendar.DAY_OF_MONTH, 31);

Then, for increasing it by 1 day, I can do 2 things :

cal.add(Calendar.DAY_OF_MONTH, 1);

OR

cal.add(Calendar.DAY_OF_YEAR, 1);

There are also other "DAY" constants, but I get the same result using the above 2 methods of increasing the day by 1. In which case will I get different results for the two?

Answer 1

For adding it really makes no difference, but this

Calendar c = Calendar.getInstance();
System.out.println(c.get(Calendar.DAY_OF_MONTH));
System.out.println(c.get(Calendar.DAY_OF_YEAR));

prints

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