Calendar DAY_OF_YEAR problem in 1.6?

[du-it]

I have a problem using the GregorianCalendar:
First I create a GregorianCalendar instance and set the day of year with value -30. That's fine.
Afterwards I uses another GregorianCalendar doing the same but setting the day of year with value -1 and the result totally differs from what I expected. Instead of subtracting one day of the GregorianCalendar's current date it sets the calendar to 30th Dec one year before:

GregorianCalendar gc = new GregorianCalendar();
gc.add(GregorianCalendar.DAY_OF_YEAR, -30);
Date startDate = gc.getTime();
System.out.println("startDate: " + startDate);               // Sat Feb 04 10:01:21 CET 2012
Date endDate = new Date();
System.out.println("endDate: " + endDate);
GregorianCalendar gc1 = new GregorianCalendar();
gc1.set(Calendar.DAY_OF_YEAR, -1);
Date endDate = gc1.getTime();
System.out.println("endDate: " + endDate);                 //  Thu Dec 30 10:01:24 CET 2011

Where am I going wrong??

[DarrylBurke]

add != set

db

[du-it]

Thank you!!!

Oha.. for the first date I did it well. (Sometimes I miss the forest for the trees.)

What is the difference between add and set in this case? Is it because the value was negative? I can't see why the result is 64. (I would have an idea of what happened if the result would be 364. Then I could guess that Calendar calculates MAX_DAYS_OF_A_YEAR plus (myMinusValue) = 364.)

However, it works now. Thank you.

[DarrylBurke]

What is the difference between add and set in this case?

In this case or any other, read the API to find what the method promises to deliver.

db