Day period incorrectly computed

The day period (@see com.xpn.xwiki.stats.impl.XWikiStats#PERIOD_DAY) is incorrectly computed in

{@link com.xpn.xwiki.stats.impl.XWikiStats#getPeriodAsInt(Date, int)}

. The problem is related to the inconsistent implementation of

{@link java.util.Calendar}

. More precisely, in Calendar we have the following:

public static final int DAY_OF_MONTH
Field number for get and set indicating the day of the month. This is a synonym for DATE. The first day of the month has value 1.

public static final int MONTH
Field number for get and set indicating the month. This is a calendar-specific value. The first month of the year is JANUARY which is 0; the last depends on the number of months in a year.

Currently, for a date like 'October 18th, 2007" the getPeriodAsInt(date, XWikiStats.PERIOD_DAY) returns 20071019, which is wrong.