Question

I wonder why ‘Y’ returns 2012 while ‘y’ returns 2011 in SimpleDateFormat:

System.out.println(new SimpleDateFormat("Y").format(new Date())); // prints 2012
System.out.println(new SimpleDateFormat("y").format(new Date())); // prints 2011

Can any one explain why?

Answer 1

week year and year. From javadoc

A week year is in sync with a WEEK_OF_YEAR cycle. All weeks between
the first and last weeks (inclusive) have the same week year value.
Therefore, the first and last days of a week year may have different
calendar year values.

For example, January 1, 1998 is a Thursday. If getFirstDayOfWeek() is
MONDAY and getMinimalDaysInFirstWeek() is 4 (ISO 8601 standard
compatible setting), then week 1 of 1998 starts on December 29, 1997,
and ends on January 4, 1998. The week year is 1998 for the last three
days of calendar year 1997. If, however, getFirstDayOfWeek() is
SUNDAY, then week 1 of 1998 starts on January 4, 1998, and ends on
January 10, 1998; the first three days of 1998 then are part of week
53 of 1997 and their week year is 1997.