Check in the pristine copy of ICU 4.6...

icu46/source/i18n/unicode/gregocal.h

+/*
+* Copyright (C) 1997-2009, International Business Machines Corporation and others.
+* All Rights Reserved.
+********************************************************************************
+*
+* File GREGOCAL.H
+*
+* Modification History:
+*
+*   Date        Name        Description
+*   04/22/97    aliu        Overhauled header.
+*    07/28/98    stephen        Sync with JDK 1.2
+*    09/04/98    stephen        Re-sync with JDK 8/31 putback
+*    09/14/98    stephen        Changed type of kOneDay, kOneWeek to double.
+*                            Fixed bug in roll()
+*   10/15/99    aliu        Fixed j31, incorrect WEEK_OF_YEAR computation.
+*                           Added documentation of WEEK_OF_YEAR computation.
+*   10/15/99    aliu        Fixed j32, cannot set date to Feb 29 2000 AD.
+*                           {JDK bug 4210209 4209272}
+*   11/07/2003  srl         Update, clean up documentation.
+********************************************************************************
+*/
+
+#ifndef GREGOCAL_H
+#define GREGOCAL_H
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_FORMATTING
+
+#include "unicode/calendar.h"
+
+/**
+ * \file 
+ * \brief C++ API: Concrete class which provides the standard calendar.
+ */
+
+U_NAMESPACE_BEGIN
+
+/** 
+ * Concrete class which provides the standard calendar used by most of the world.
+ * <P>
+ * The standard (Gregorian) calendar has 2 eras, BC and AD.
+ * <P>
+ * This implementation handles a single discontinuity, which corresponds by default to
+ * the date the Gregorian calendar was originally instituted (October 15, 1582). Not all
+ * countries adopted the Gregorian calendar then, so this cutover date may be changed by
+ * the caller.
+ * <P>
+ * Prior to the institution of the Gregorian Calendar, New Year's Day was March 25. To
+ * avoid confusion, this Calendar always uses January 1. A manual adjustment may be made
+ * if desired for dates that are prior to the Gregorian changeover and which fall
+ * between January 1 and March 24.
+ *
+ * <p>Values calculated for the <code>WEEK_OF_YEAR</code> field range from 1 to
+ * 53.  Week 1 for a year is the first week that contains at least
+ * <code>getMinimalDaysInFirstWeek()</code> days from that year.  It thus
+ * depends on the values of <code>getMinimalDaysInFirstWeek()</code>,
+ * <code>getFirstDayOfWeek()</code>, and the day of the week of January 1.
+ * Weeks between week 1 of one year and week 1 of the following year are
+ * numbered sequentially from 2 to 52 or 53 (as needed).
+ *
+ * <p>For example, January 1, 1998 was a Thursday.  If
+ * <code>getFirstDayOfWeek()</code> is <code>MONDAY</code> and
+ * <code>getMinimalDaysInFirstWeek()</code> is 4 (these are the values
+ * reflecting ISO 8601 and many national standards), then week 1 of 1998 starts
+ * on December 29, 1997, and ends on January 4, 1998.  If, however,
+ * <code>getFirstDayOfWeek()</code> is <code>SUNDAY</code>, 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.
+ *
+ * <p>Example for using GregorianCalendar:
+ * <pre>
+ * \code
+ *     // get the supported ids for GMT-08:00 (Pacific Standard Time)
+ *     UErrorCode success = U_ZERO_ERROR;
+ *     const StringEnumeration *ids = TimeZone::createEnumeration(-8 * 60 * 60 * 1000);
+ *     // if no ids were returned, something is wrong. get out.
+ *     if (ids == 0 || ids->count(success) == 0) {
+ *         return;
+ *     }
+ *
+ *     // begin output
+ *     cout << "Current Time" << endl;
+ *
+ *     // create a Pacific Standard Time time zone
+ *     SimpleTimeZone* pdt = new SimpleTimeZone(-8 * 60 * 60 * 1000, ids->unext(NULL, success)));
+ *
+ *     // set up rules for daylight savings time
+ *     pdt->setStartRule(UCAL_MARCH, 1, UCAL_SUNDAY, 2 * 60 * 60 * 1000);
+ *     pdt->setEndRule(UCAL_NOVEMBER, 2, UCAL_SUNDAY, 2 * 60 * 60 * 1000);
+ *
+ *     // create a GregorianCalendar with the Pacific Daylight time zone
+ *     // and the current date and time
+ *     Calendar* calendar = new GregorianCalendar( pdt, success );
+ *
+ *     // print out a bunch of interesting things
+ *     cout << "ERA: " << calendar->get( UCAL_ERA, success ) << endl;
+ *     cout << "YEAR: " << calendar->get( UCAL_YEAR, success ) << endl;
+ *     cout << "MONTH: " << calendar->get( UCAL_MONTH, success ) << endl;
+ *     cout << "WEEK_OF_YEAR: " << calendar->get( UCAL_WEEK_OF_YEAR, success ) << endl;
+ *     cout << "WEEK_OF_MONTH: " << calendar->get( UCAL_WEEK_OF_MONTH, success ) << endl;
+ *     cout << "DATE: " << calendar->get( UCAL_DATE, success ) << endl;
+ *     cout << "DAY_OF_MONTH: " << calendar->get( UCAL_DAY_OF_MONTH, success ) << endl;
+ *     cout << "DAY_OF_YEAR: " << calendar->get( UCAL_DAY_OF_YEAR, success ) << endl;
+ *     cout << "DAY_OF_WEEK: " << calendar->get( UCAL_DAY_OF_WEEK, success ) << endl;
+ *     cout << "DAY_OF_WEEK_IN_MONTH: " << calendar->get( UCAL_DAY_OF_WEEK_IN_MONTH, success ) << endl;
+ *     cout << "AM_PM: " << calendar->get( UCAL_AM_PM, success ) << endl;
+ *     cout << "HOUR: " << calendar->get( UCAL_HOUR, success ) << endl;
+ *     cout << "HOUR_OF_DAY: " << calendar->get( UCAL_HOUR_OF_DAY, success ) << endl;
+ *     cout << "MINUTE: " << calendar->get( UCAL_MINUTE, success ) << endl;
+ *     cout << "SECOND: " << calendar->get( UCAL_SECOND, success ) << endl;
+ *     cout << "MILLISECOND: " << calendar->get( UCAL_MILLISECOND, success ) << endl;
+ *     cout << "ZONE_OFFSET: " << (calendar->get( UCAL_ZONE_OFFSET, success )/(60*60*1000)) << endl;
+ *     cout << "DST_OFFSET: " << (calendar->get( UCAL_DST_OFFSET, success )/(60*60*1000)) << endl;
+ *
+ *     cout << "Current Time, with hour reset to 3" << endl;
+ *     calendar->clear(UCAL_HOUR_OF_DAY); // so doesn't override
+ *     calendar->set(UCAL_HOUR, 3);
+ *     cout << "ERA: " << calendar->get( UCAL_ERA, success ) << endl;
+ *     cout << "YEAR: " << calendar->get( UCAL_YEAR, success ) << endl;
+ *     cout << "MONTH: " << calendar->get( UCAL_MONTH, success ) << endl;
+ *     cout << "WEEK_OF_YEAR: " << calendar->get( UCAL_WEEK_OF_YEAR, success ) << endl;
+ *     cout << "WEEK_OF_MONTH: " << calendar->get( UCAL_WEEK_OF_MONTH, success ) << endl;
+ *     cout << "DATE: " << calendar->get( UCAL_DATE, success ) << endl;
+ *     cout << "DAY_OF_MONTH: " << calendar->get( UCAL_DAY_OF_MONTH, success ) << endl;
+ *     cout << "DAY_OF_YEAR: " << calendar->get( UCAL_DAY_OF_YEAR, success ) << endl;
+ *     cout << "DAY_OF_WEEK: " << calendar->get( UCAL_DAY_OF_WEEK, success ) << endl;
+ *     cout << "DAY_OF_WEEK_IN_MONTH: " << calendar->get( UCAL_DAY_OF_WEEK_IN_MONTH, success ) << endl;
+ *     cout << "AM_PM: " << calendar->get( UCAL_AM_PM, success ) << endl;
+ *     cout << "HOUR: " << calendar->get( UCAL_HOUR, success ) << endl;
+ *     cout << "HOUR_OF_DAY: " << calendar->get( UCAL_HOUR_OF_DAY, success ) << endl;
+ *     cout << "MINUTE: " << calendar->get( UCAL_MINUTE, success ) << endl;
+ *     cout << "SECOND: " << calendar->get( UCAL_SECOND, success ) << endl;
+ *     cout << "MILLISECOND: " << calendar->get( UCAL_MILLISECOND, success ) << endl;
+ *     cout << "ZONE_OFFSET: " << (calendar->get( UCAL_ZONE_OFFSET, success )/(60*60*1000)) << endl; // in hours
+ *     cout << "DST_OFFSET: " << (calendar->get( UCAL_DST_OFFSET, success )/(60*60*1000)) << endl; // in hours
+ *
+ *     if (U_FAILURE(success)) {
+ *         cout << "An error occured. success=" << u_errorName(success) << endl;
+ *     }
+ *
+ *     delete ids;
+ *     delete calendar; // also deletes pdt
+ * \endcode
+ * </pre>
+ * @stable ICU 2.0
+ */
+class U_I18N_API GregorianCalendar: public Calendar {
+public:
+
+    /**
+     * Useful constants for GregorianCalendar and TimeZone.
+     * @stable ICU 2.0
+     */
+    enum EEras {
+        BC,
+        AD
+    };
+
+    /**
+     * Constructs a default GregorianCalendar using the current time in the default time
+     * zone with the default locale.
+     *
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar based on the current time in the given time zone
+     * with the default locale. Clients are no longer responsible for deleting the given
+     * time zone object after it's adopted.
+     *
+     * @param zoneToAdopt     The given timezone.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(TimeZone* zoneToAdopt, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar based on the current time in the given time zone
+     * with the default locale.
+     *
+     * @param zone     The given timezone.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(const TimeZone& zone, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar based on the current time in the default time zone
+     * with the given locale.
+     *
+     * @param aLocale  The given locale.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar based on the current time in the given time zone
+     * with the given locale. Clients are no longer responsible for deleting the given
+     * time zone object after it's adopted.
+     *
+     * @param zoneToAdopt     The given timezone.
+     * @param aLocale  The given locale.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(TimeZone* zoneToAdopt, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar based on the current time in the given time zone
+     * with the given locale.
+     *
+     * @param zone     The given timezone.
+     * @param aLocale  The given locale.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(const TimeZone& zone, const Locale& aLocale, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar with the given AD date set in the default time
+     * zone with the default locale.
+     *
+     * @param year     The value used to set the YEAR time field in the calendar.
+     * @param month    The value used to set the MONTH time field in the calendar. Month
+     *                 value is 0-based. e.g., 0 for January.
+     * @param date     The value used to set the DATE time field in the calendar.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(int32_t year, int32_t month, int32_t date, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar with the given AD date and time set for the
+     * default time zone with the default locale.
+     *
+     * @param year     The value used to set the YEAR time field in the calendar.
+     * @param month    The value used to set the MONTH time field in the calendar. Month
+     *                 value is 0-based. e.g., 0 for January.
+     * @param date     The value used to set the DATE time field in the calendar.
+     * @param hour     The value used to set the HOUR_OF_DAY time field in the calendar.
+     * @param minute   The value used to set the MINUTE time field in the calendar.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(int32_t year, int32_t month, int32_t date, int32_t hour, int32_t minute, UErrorCode& success);
+
+    /**
+     * Constructs a GregorianCalendar with the given AD date and time set for the
+     * default time zone with the default locale.
+     *
+     * @param year     The value used to set the YEAR time field in the calendar.
+     * @param month    The value used to set the MONTH time field in the calendar. Month
+     *                 value is 0-based. e.g., 0 for January.
+     * @param date     The value used to set the DATE time field in the calendar.
+     * @param hour     The value used to set the HOUR_OF_DAY time field in the calendar.
+     * @param minute   The value used to set the MINUTE time field in the calendar.
+     * @param second   The value used to set the SECOND time field in the calendar.
+     * @param success  Indicates the status of GregorianCalendar object construction.
+     *                 Returns U_ZERO_ERROR if constructed successfully.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(int32_t year, int32_t month, int32_t date, int32_t hour, int32_t minute, int32_t second, UErrorCode& success);
+
+    /**
+     * Destructor
+     * @stable ICU 2.0
+     */
+    virtual ~GregorianCalendar();
+
+    /**
+     * Copy constructor
+     * @param source    the object to be copied.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar(const GregorianCalendar& source);
+
+    /**
+     * Default assignment operator
+     * @param right    the object to be copied.
+     * @stable ICU 2.0
+     */
+    GregorianCalendar& operator=(const GregorianCalendar& right);
+
+    /**
+     * Create and return a polymorphic copy of this calendar.
+     * @return    return a polymorphic copy of this calendar.
+     * @stable ICU 2.0
+     */
+    virtual Calendar* clone(void) const;
+
+    /**
+     * Sets the GregorianCalendar change date. This is the point when the switch from
+     * Julian dates to Gregorian dates occurred. Default is 00:00:00 local time, October
+     * 15, 1582. Previous to this time and date will be Julian dates.
+     *
+     * @param date     The given Gregorian cutover date.
+     * @param success  Output param set to success/failure code on exit.
+     * @stable ICU 2.0
+     */
+    void setGregorianChange(UDate date, UErrorCode& success);
+
+    /**
+     * Gets the Gregorian Calendar change date. This is the point when the switch from
+     * Julian dates to Gregorian dates occurred. Default is 00:00:00 local time, October
+     * 15, 1582. Previous to this time and date will be Julian dates.
+     *
+     * @return   The Gregorian cutover time for this calendar.
+     * @stable ICU 2.0
+     */
+    UDate getGregorianChange(void) const;
+
+    /**
+     * Return true if the given year is a leap year. Determination of whether a year is
+     * a leap year is actually very complicated. We do something crude and mostly
+     * correct here, but for a real determination you need a lot of contextual
+     * information. For example, in Sweden, the change from Julian to Gregorian happened
+     * in a complex way resulting in missed leap years and double leap years between
+     * 1700 and 1753. Another example is that after the start of the Julian calendar in
+     * 45 B.C., the leap years did not regularize until 8 A.D. This method ignores these
+     * quirks, and pays attention only to the Julian onset date and the Gregorian
+     * cutover (which can be changed).
+     *
+     * @param year  The given year.
+     * @return      True if the given year is a leap year; false otherwise.
+     * @stable ICU 2.0
+     */
+    UBool isLeapYear(int32_t year) const;
+
+    /**
+     * Returns TRUE if the given Calendar object is equivalent to this
+     * one.  Calendar override.
+     *
+     * @param other the Calendar to be compared with this Calendar   
+     * @stable ICU 2.4
+     */
+    virtual UBool isEquivalentTo(const Calendar& other) const;
+
+    /**
+     * (Overrides Calendar) Rolls up or down by the given amount in the specified field.
+     * For more information, see the documentation for Calendar::roll().
+     *
+     * @param field   The time field.
+     * @param amount  Indicates amount to roll.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @deprecated ICU 2.6. Use roll(UCalendarDateFields field, int32_t amount, UErrorCode& status) instead.
+     */
+    virtual void roll(EDateFields field, int32_t amount, UErrorCode& status);
+
+    /**
+     * (Overrides Calendar) Rolls up or down by the given amount in the specified field.
+     * For more information, see the documentation for Calendar::roll().
+     *
+     * @param field   The time field.
+     * @param amount  Indicates amount to roll.
+     * @param status  Output param set to success/failure code on exit. If any value
+     *                previously set in the time field is invalid, this will be set to
+     *                an error status.
+     * @stable ICU 2.6.
+     */
+    virtual void roll(UCalendarDateFields field, int32_t amount, UErrorCode& status);
+
+    /**
+     * Return the minimum value that this field could have, given the current date.
+     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
+     * @param field    the time field.
+     * @return         the minimum value that this field could have, given the current date.
+     * @deprecated ICU 2.6. Use getActualMinimum(UCalendarDateFields field) instead.
+     */
+    int32_t getActualMinimum(EDateFields field) const;
+
+    /**
+     * Return the minimum value that this field could have, given the current date.
+     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
+     * @param field    the time field.
+     * @param status
+     * @return         the minimum value that this field could have, given the current date.
+     * @deprecated ICU 2.6. Use getActualMinimum(UCalendarDateFields field) instead. (Added to ICU 3.0 for signature consistency)
+     */
+    int32_t getActualMinimum(EDateFields field, UErrorCode& status) const;
+
+    /**
+     * Return the minimum value that this field could have, given the current date.
+     * For the Gregorian calendar, this is the same as getMinimum() and getGreatestMinimum().
+     * @param field    the time field.
+     * @param status   error result.
+     * @return         the minimum value that this field could have, given the current date.
+     * @stable ICU 3.0
+     */
+    int32_t getActualMinimum(UCalendarDateFields field, UErrorCode &status) const;
+
+    /**
+     * Return the maximum value that this field could have, given the current date.
+     * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
+     * maximum would be 28; for "Feb 3, 1996" it s 29.  Similarly for a Hebrew calendar,
+     * for some years the actual maximum for MONTH is 12, and for others 13.
+     * @param field    the time field.
+     * @return         the maximum value that this field could have, given the current date.
+     * @deprecated ICU 2.6. Use getActualMaximum(UCalendarDateFields field) instead.
+     */
+    int32_t getActualMaximum(EDateFields field) const;
+
+    /**
+     * Return the maximum value that this field could have, given the current date.
+     * For example, with the date "Feb 3, 1997" and the DAY_OF_MONTH field, the actual
+     * maximum would be 28; for "Feb 3, 1996" it s 29.  Similarly for a Hebrew calendar,
+     * for some years the actual maximum for MONTH is 12, and for others 13.
+     * @param field    the time field.
+     * @param status   returns any errors that may result from this function call.
+     * @return         the maximum value that this field could have, given the current date.
+     * @stable ICU 2.6
+     */
+    virtual int32_t getActualMaximum(UCalendarDateFields field, UErrorCode& status) const;
+
+    /**
+     * (Overrides Calendar) Return true if the current date for this Calendar is in
+     * Daylight Savings Time. Recognizes DST_OFFSET, if it is set.
+     *
+     * @param status Fill-in parameter which receives the status of this operation.
+     * @return   True if the current date for this Calendar is in Daylight Savings Time,
+     *           false, otherwise.
+     * @stable ICU 2.0
+     */
+    virtual UBool inDaylightTime(UErrorCode& status) const;
+
+public:
+
+    /**
+     * Override Calendar Returns a unique class ID POLYMORPHICALLY. Pure virtual
+     * override. This method is to implement a simple version of RTTI, since not all C++
+     * compilers support genuine RTTI. Polymorphic operator==() and clone() methods call
+     * this method.
+     *
+     * @return   The class ID for this object. All objects of a given class have the
+     *           same class ID. Objects of other classes have different class IDs.
+     * @stable ICU 2.0
+     */
+    virtual UClassID getDynamicClassID(void) const;
+
+    /**
+     * Return the class ID for this class. This is useful only for comparing to a return
+     * value from getDynamicClassID(). For example:
+     *
+     *      Base* polymorphic_pointer = createPolymorphicObject();
+     *      if (polymorphic_pointer->getDynamicClassID() ==
+     *          Derived::getStaticClassID()) ...
+     *
+     * @return   The class ID for all objects of this class.
+     * @stable ICU 2.0
+     */
+    static UClassID U_EXPORT2 getStaticClassID(void);
+
+    /**
+     * Get the calendar type, "gregorian", for use in DateFormatSymbols.
+     *
+     * @return calendar type
+     * @internal
+     */
+    virtual const char * getType() const;
+
+protected:
+
+    /**
+     * (Overrides Calendar) Converts GMT as milliseconds to time field values.
+     * @param status Fill-in parameter which receives the status of this operation.
+     * @stable ICU 2.0
+     */
+
+ private:
+    GregorianCalendar(); // default constructor not implemented
+
+ protected:
+    /**
+     * Return the ERA.  We need a special method for this because the
+     * default ERA is AD, but a zero (unset) ERA is BC.
+     * @return    the ERA.
+     * @internal
+     */
+    virtual int32_t internalGetEra() const;
+
+    /**
+     * Return the Julian day number of day before the first day of the
+     * given month in the given extended year.  Subclasses should override
+     * this method to implement their calendar system.
+     * @param eyear the extended year
+     * @param month the zero-based month, or 0 if useMonth is false
+     * @param useMonth if false, compute the day before the first day of
+     * the given year, otherwise, compute the day before the first day of
+     * the given month
+     * @return the Julian day number of the day before the first
+     * day of the given month and year
+     * @internal
+     */
+    virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month,
+                                                   UBool useMonth) const;
+
+    /**
+     * Subclasses may override this.  This method calls
+     * handleGetMonthLength() to obtain the calendar-specific month
+     * length.
+     * @param bestField which field to use to calculate the date 
+     * @return julian day specified by calendar fields.
+     * @internal
+     */
+    virtual int32_t handleComputeJulianDay(UCalendarDateFields bestField)  ;
+
+    /**
+     * Return the number of days in the given month of the given extended
+     * year of this calendar system.  Subclasses should override this
+     * method if they can provide a more correct or more efficient
+     * implementation than the default implementation in Calendar.
+     * @internal
+     */
+    virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const;
+
+    /**
+     * Return the number of days in the given extended year of this
+     * calendar system.  Subclasses should override this method if they can
+     * provide a more correct or more efficient implementation than the
+     * default implementation in Calendar.
+     * @stable ICU 2.0
+     */
+    virtual int32_t handleGetYearLength(int32_t eyear) const;
+
+    /**
+     * return the length of the given month.
+     * @param month    the given month.
+     * @return    the length of the given month.
+     * @internal
+     */
+    virtual int32_t monthLength(int32_t month) const;
+
+    /**
+     * return the length of the month according to the given year.
+     * @param month    the given month.
+     * @param year     the given year.
+     * @return         the length of the month
+     * @internal
+     */
+    virtual int32_t monthLength(int32_t month, int32_t year) const;
+    
+    /**
+     * return the length of the given year.
+     * @param year    the given year.
+     * @return        the length of the given year.
+     * @internal
+     */
+    int32_t yearLength(int32_t year) const;
+    
+    /**
+     * return the length of the year field.
+     * @return    the length of the year field
+     * @internal
+     */
+    int32_t yearLength(void) const;
+
+    /**
+     * After adjustments such as add(MONTH), add(YEAR), we don't want the
+     * month to jump around.  E.g., we don't want Jan 31 + 1 month to go to Mar
+     * 3, we want it to go to Feb 28.  Adjustments which might run into this
+     * problem call this method to retain the proper month.
+     * @internal
+     */
+    void pinDayOfMonth(void);
+
+    /**
+     * Return the day number with respect to the epoch.  January 1, 1970 (Gregorian)
+     * is day zero.
+     * @param status Fill-in parameter which receives the status of this operation.
+     * @return       the day number with respect to the epoch.  
+     * @internal
+     */
+    virtual UDate getEpochDay(UErrorCode& status);
+
+    /**
+     * Subclass API for defining limits of different types.
+     * Subclasses must implement this method to return limits for the
+     * following fields:
+     *
+     * <pre>UCAL_ERA
+     * UCAL_YEAR
+     * UCAL_MONTH
+     * UCAL_WEEK_OF_YEAR
+     * UCAL_WEEK_OF_MONTH
+     * UCAL_DATE (DAY_OF_MONTH on Java)
+     * UCAL_DAY_OF_YEAR
+     * UCAL_DAY_OF_WEEK_IN_MONTH
+     * UCAL_YEAR_WOY
+     * UCAL_EXTENDED_YEAR</pre>
+     *
+     * @param field one of the above field numbers
+     * @param limitType one of <code>MINIMUM</code>, <code>GREATEST_MINIMUM</code>,
+     * <code>LEAST_MAXIMUM</code>, or <code>MAXIMUM</code>
+     * @internal
+     */
+    virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const;
+
+    /**
+     * Return the extended year defined by the current fields.  This will
+     * use the UCAL_EXTENDED_YEAR field or the UCAL_YEAR and supra-year fields (such
+     * as UCAL_ERA) specific to the calendar system, depending on which set of
+     * fields is newer.
+     * @return the extended year
+     * @internal
+     */
+    virtual int32_t handleGetExtendedYear();
+
+    /** 
+     * Subclasses may override this to convert from week fields 
+     * (YEAR_WOY and WEEK_OF_YEAR) to an extended year in the case
+     * where YEAR, EXTENDED_YEAR are not set.
+     * The Gregorian implementation assumes a yearWoy in gregorian format, according to the current era.
+     * @return the extended year, UCAL_EXTENDED_YEAR
+     * @internal
+     */
+    virtual int32_t handleGetExtendedYearFromWeekFields(int32_t yearWoy, int32_t woy);
+
+
+    /**
+     * Subclasses may override this method to compute several fields
+     * specific to each calendar system.  These are:
+     *
+     * <ul><li>ERA
+     * <li>YEAR
+     * <li>MONTH
+     * <li>DAY_OF_MONTH
+     * <li>DAY_OF_YEAR
+     * <li>EXTENDED_YEAR</ul>
+     *
+     * <p>The GregorianCalendar implementation implements
+     * a calendar with the specified Julian/Gregorian cutover date.
+     * @internal
+     */
+    virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
+
+ private:
+    /**
+     * Compute the julian day number of the given year.
+     * @param isGregorian    if true, using Gregorian calendar, otherwise using Julian calendar
+     * @param year           the given year.
+     * @param isLeap         true if the year is a leap year.       
+     * @return 
+     */
+    static double computeJulianDayOfYear(UBool isGregorian, int32_t year,
+                                         UBool& isLeap);
+    
+    /**
+     * Validates the values of the set time fields.  True if they're all valid.
+     * @return    True if the set time fields are all valid.
+     */
+    UBool validateFields(void) const;
+
+    /**
+     * Validates the value of the given time field.  True if it's valid.
+     */
+    UBool boundsCheck(int32_t value, UCalendarDateFields field) const;
+
+    /**
+     * Return the pseudo-time-stamp for two fields, given their
+     * individual pseudo-time-stamps.  If either of the fields
+     * is unset, then the aggregate is unset.  Otherwise, the
+     * aggregate is the later of the two stamps.
+     * @param stamp_a    One given field.
+     * @param stamp_b    Another given field.
+     * @return the pseudo-time-stamp for two fields
+     */
+    int32_t aggregateStamp(int32_t stamp_a, int32_t stamp_b);
+
+    /**
+     * The point at which the Gregorian calendar rules are used, measured in
+     * milliseconds from the standard epoch.  Default is October 15, 1582
+     * (Gregorian) 00:00:00 UTC, that is, October 4, 1582 (Julian) is followed
+     * by October 15, 1582 (Gregorian).  This corresponds to Julian day number
+     * 2299161. This is measured from the standard epoch, not in Julian Days.
+     * @internal
+     */
+    UDate                fGregorianCutover;
+
+    /**
+     * Julian day number of the Gregorian cutover
+     */
+    int32_t             fCutoverJulianDay;
+
+    /**
+     * Midnight, local time (using this Calendar's TimeZone) at or before the
+     * gregorianCutover. This is a pure date value with no time of day or
+     * timezone component.
+     */
+    UDate                 fNormalizedGregorianCutover;// = gregorianCutover;
+
+    /**
+     * The year of the gregorianCutover, with 0 representing
+     * 1 BC, -1 representing 2 BC, etc.
+     */
+    int32_t fGregorianCutoverYear;// = 1582;
+
+    /**
+     * The year of the gregorianCutover, with 0 representing
+     * 1 BC, -1 representing 2 BC, etc.
+     */
+    int32_t fGregorianCutoverJulianDay;// = 2299161;
+
+    /**
+     * Converts time as milliseconds to Julian date. The Julian date used here is not a
+     * true Julian date, since it is measured from midnight, not noon.
+     *
+     * @param millis  The given milliseconds.
+     * @return        The Julian date number.
+     */
+    static double millisToJulianDay(UDate millis);
+
+    /**
+     * Converts Julian date to time as milliseconds. The Julian date used here is not a
+     * true Julian date, since it is measured from midnight, not noon.
+     *
+     * @param julian  The given Julian date number.
+     * @return        Time as milliseconds.
+     */
+    static UDate julianDayToMillis(double julian);
+
+    /**
+     * Used by handleComputeJulianDay() and handleComputeMonthStart().
+     * Temporary field indicating whether the calendar is currently Gregorian as opposed to Julian.
+     */
+    UBool fIsGregorian;
+
+    /**
+     * Used by handleComputeJulianDay() and handleComputeMonthStart().
+     * Temporary field indicating that the sense of the gregorian cutover should be inverted
+     * to handle certain calculations on and around the cutover date.
+     */
+    UBool fInvertGregorian;
+
+
+ public: // internal implementation
+
+    /**
+     * @internal 
+     * @return TRUE if this calendar has the notion of a default century
+     */
+    virtual UBool haveDefaultCentury() const;
+
+    /**
+     * @internal
+     * @return the start of the default century
+     */
+    virtual UDate defaultCenturyStart() const;
+
+    /**
+     * @internal 
+     * @return the beginning year of the default century
+     */
+    virtual int32_t defaultCenturyStartYear() const;
+
+ private:
+    /**
+     * The system maintains a static default century start date.  This is initialized
+     * the first time it is used.  Before then, it is set to SYSTEM_DEFAULT_CENTURY to
+     * indicate an uninitialized state.  Once the system default century date and year
+     * are set, they do not change.
+     */
+    static UDate         fgSystemDefaultCenturyStart;
+
+    /**
+     * See documentation for systemDefaultCenturyStart.
+     */
+    static int32_t          fgSystemDefaultCenturyStartYear;
+
+    /**
+     * Default value that indicates the defaultCenturyStartYear is unitialized
+     */
+    static const int32_t    fgSystemDefaultCenturyYear;
+
+    /**
+     * Default value that indicates the UDate of the beginning of the system default century
+     */
+    static const UDate        fgSystemDefaultCentury;
+
+    /**
+     * Returns the beginning date of the 100-year window that dates with 2-digit years
+     * are considered to fall within.
+     * @return    the beginning date of the 100-year window that dates with 2-digit years
+     *            are considered to fall within.
+     */
+    UDate         internalGetDefaultCenturyStart(void) const;
+
+    /**
+     * Returns the first year of the 100-year window that dates with 2-digit years
+     * are considered to fall within.
+     * @return    the first year of the 100-year window that dates with 2-digit years
+     *            are considered to fall within.
+     */
+    int32_t          internalGetDefaultCenturyStartYear(void) const;
+
+    /**
+     * Initializes the 100-year window that dates with 2-digit years are considered
+     * to fall within so that its start date is 80 years before the current time.
+     */
+    static void  initializeSystemDefaultCentury(void);
+
+};
+
+U_NAMESPACE_END
+
+#endif /* #if !UCONFIG_NO_FORMATTING */
+
+#endif // _GREGOCAL
+//eof
+