add more than 30 days with Calendar's add() method in Java

Question

Hi,

I'm not quite sure what field to use when adding more than 30 days to a Java Calendar object. Is there any difference in between Calendar.DAY_OF_MONTH and Calendar.DAY_OF_YEAR?

Example:

GregorianCalendar d = new GregorianCalendar();
d.add(Calendar.DAY_OF_YEAR, 90);

vs

GregorianCalendar d = new GregorianCalendar();
d.add(Calendar.DAY_OF_MONTH, 90);

Thanks.

Answer 1

I don't think it makes a difference when you call add. The distinction is important when you call the getters.

Both methods work fine, right? For more than 30 days, as well as negative amounts.

The (admittedly complicated) source for GregorianCalendar#add has this section:

 case DAY_OF_MONTH: // synonym of DATE
 case DAY_OF_YEAR:
 case DAY_OF_WEEK:
    break;