1/*
2 ********************************************************************************
3 * Copyright (C) 2003-2013, International Business Machines Corporation
4 * and others. All Rights Reserved.
5 ******************************************************************************
6 *
7 * File ISLAMCAL.H
8 *
9 * Modification History:
10 *
11 *   Date        Name        Description
12 *   10/14/2003  srl         ported from java IslamicCalendar
13 *****************************************************************************
14 */
15
16#ifndef ISLAMCAL_H
17#define ISLAMCAL_H
18
19#include "unicode/utypes.h"
20
21#if !UCONFIG_NO_FORMATTING
22
23#include "unicode/calendar.h"
24
25U_NAMESPACE_BEGIN
26
27/**
28 * <code>IslamicCalendar</code> is a subclass of <code>Calendar</code>
29 * that implements the Islamic civil and religious calendars.  It
30 * is used as the civil calendar in most of the Arab world and the
31 * liturgical calendar of the Islamic faith worldwide.  This calendar
32 * is also known as the "Hijri" calendar, since it starts at the time
33 * of Mohammed's emigration (or "hijra") to Medinah on Thursday,
34 * July 15, 622 AD (Julian).
35 * <p>
36 * The Islamic calendar is strictly lunar, and thus an Islamic year of twelve
37 * lunar months does not correspond to the solar year used by most other
38 * calendar systems, including the Gregorian.  An Islamic year is, on average,
39 * about 354 days long, so each successive Islamic year starts about 11 days
40 * earlier in the corresponding Gregorian year.
41 * <p>
42 * Each month of the calendar starts when the new moon's crescent is visible
43 * at sunset.  However, in order to keep the time fields in this class
44 * synchronized with those of the other calendars and with local clock time,
45 * we treat days and months as beginning at midnight,
46 * roughly 6 hours after the corresponding sunset.
47 * <p>
48 * There are two main variants of the Islamic calendar in existence.  The first
49 * is the <em>civil</em> calendar, which uses a fixed cycle of alternating 29-
50 * and 30-day months, with a leap day added to the last month of 11 out of
51 * every 30 years.  This calendar is easily calculated and thus predictable in
52 * advance, so it is used as the civil calendar in a number of Arab countries.
53 * This is the default behavior of a newly-created <code>IslamicCalendar</code>
54 * object.
55 * <p>
56 * The Islamic <em>religious</em> calendar, however, is based on the <em>observation</em>
57 * of the crescent moon.  It is thus affected by the position at which the
58 * observations are made, seasonal variations in the time of sunset, the
59 * eccentricities of the moon's orbit, and even the weather at the observation
60 * site.  This makes it impossible to calculate in advance, and it causes the
61 * start of a month in the religious calendar to differ from the civil calendar
62 * by up to three days.
63 * <p>
64 * Using astronomical calculations for the position of the sun and moon, the
65 * moon's illumination, and other factors, it is possible to determine the start
66 * of a lunar month with a fairly high degree of certainty.  However, these
67 * calculations are extremely complicated and thus slow, so most algorithms,
68 * including the one used here, are only approximations of the true astronical
69 * calculations.  At present, the approximations used in this class are fairly
70 * simplistic; they will be improved in later versions of the code.
71 * <p>
72 * The {@link #setCivil setCivil} method determines
73 * which approach is used to determine the start of a month.  By default, the
74 * fixed-cycle civil calendar is used.  However, if <code>setCivil(false)</code>
75 * is called, an approximation of the true lunar calendar will be used.
76 *
77 * @see GregorianCalendar
78 *
79 * @author Laura Werner
80 * @author Alan Liu
81 * @author Steven R. Loomis
82 * @internal
83 */
84class U_I18N_API IslamicCalendar : public Calendar {
85 public:
86  //-------------------------------------------------------------------------
87  // Constants...
88  //-------------------------------------------------------------------------
89
90  /**
91   * Calendar type - civil or religious or um alqura
92   * @internal
93   */
94  enum ECalculationType {
95    ASTRONOMICAL,
96    CIVIL,
97    UMALQURA,
98    TBLA
99  };
100
101  /**
102   * Constants for the months
103   * @internal
104   */
105  enum EMonths {
106    /**
107     * Constant for Muharram, the 1st month of the Islamic year.
108     * @internal
109     */
110    MUHARRAM = 0,
111
112    /**
113     * Constant for Safar, the 2nd month of the Islamic year.
114     * @internal
115     */
116    SAFAR = 1,
117
118    /**
119     * Constant for Rabi' al-awwal (or Rabi' I), the 3rd month of the Islamic year.
120     * @internal
121     */
122    RABI_1 = 2,
123
124    /**
125     * Constant for Rabi' al-thani or (Rabi' II), the 4th month of the Islamic year.
126     * @internal
127     */
128    RABI_2 = 3,
129
130    /**
131     * Constant for Jumada al-awwal or (Jumada I), the 5th month of the Islamic year.
132     * @internal
133     */
134    JUMADA_1 = 4,
135
136    /**
137     * Constant for Jumada al-thani or (Jumada II), the 6th month of the Islamic year.
138     * @internal
139     */
140    JUMADA_2 = 5,
141
142    /**
143     * Constant for Rajab, the 7th month of the Islamic year.
144     * @internal
145     */
146    RAJAB = 6,
147
148    /**
149     * Constant for Sha'ban, the 8th month of the Islamic year.
150     * @internal
151     */
152    SHABAN = 7,
153
154    /**
155     * Constant for Ramadan, the 9th month of the Islamic year.
156     * @internal
157     */
158    RAMADAN = 8,
159
160    /**
161     * Constant for Shawwal, the 10th month of the Islamic year.
162     * @internal
163     */
164    SHAWWAL = 9,
165
166    /**
167     * Constant for Dhu al-Qi'dah, the 11th month of the Islamic year.
168     * @internal
169     */
170    DHU_AL_QIDAH = 10,
171
172    /**
173     * Constant for Dhu al-Hijjah, the 12th month of the Islamic year.
174     * @internal
175     */
176    DHU_AL_HIJJAH = 11,
177
178    ISLAMIC_MONTH_MAX
179  };
180
181
182  //-------------------------------------------------------------------------
183  // Constructors...
184  //-------------------------------------------------------------------------
185
186  /**
187   * Constructs an IslamicCalendar based on the current time in the default time zone
188   * with the given locale.
189   *
190   * @param aLocale  The given locale.
191   * @param success  Indicates the status of IslamicCalendar object construction.
192   *                 Returns U_ZERO_ERROR if constructed successfully.
193   * @param type     The Islamic calendar calculation type. The default value is CIVIL.
194   * @internal
195   */
196  IslamicCalendar(const Locale& aLocale, UErrorCode &success, ECalculationType type = CIVIL);
197
198  /**
199   * Copy Constructor
200   * @internal
201   */
202  IslamicCalendar(const IslamicCalendar& other);
203
204  /**
205   * Destructor.
206   * @internal
207   */
208  virtual ~IslamicCalendar();
209
210  /**
211   * Sets Islamic calendar calculation type used by this instance.
212   *
213   * @param type    The calendar calculation type, <code>CIVIL</code> to use the civil
214   *                calendar, <code>ASTRONOMICAL</code> to use the astronomical calendar.
215   * @internal
216   */
217  void setCalculationType(ECalculationType type, UErrorCode &status);
218
219  /**
220   * Returns <code>true</code> if this object is using the fixed-cycle civil
221   * calendar, or <code>false</code> if using the religious, astronomical
222   * calendar.
223   * @internal
224   */
225  UBool isCivil();
226
227
228  // TODO: copy c'tor, etc
229
230  // clone
231  virtual Calendar* clone() const;
232
233 private:
234  /**
235   * Determine whether a year is a leap year in the Islamic civil calendar
236   */
237  static UBool civilLeapYear(int32_t year);
238
239  /**
240   * Return the day # on which the given year starts.  Days are counted
241   * from the Hijri epoch, origin 0.
242   */
243  int32_t yearStart(int32_t year) const;
244
245  /**
246   * Return the day # on which the given month starts.  Days are counted
247   * from the Hijri epoch, origin 0.
248   *
249   * @param year  The hijri year
250   * @param year  The hijri month, 0-based
251   */
252  int32_t monthStart(int32_t year, int32_t month) const;
253
254  /**
255   * Find the day number on which a particular month of the true/lunar
256   * Islamic calendar starts.
257   *
258   * @param month The month in question, origin 0 from the Hijri epoch
259   *
260   * @return The day number on which the given month starts.
261   */
262  int32_t trueMonthStart(int32_t month) const;
263
264  /**
265   * Return the "age" of the moon at the given time; this is the difference
266   * in ecliptic latitude between the moon and the sun.  This method simply
267   * calls CalendarAstronomer.moonAge, converts to degrees,
268   * and adjusts the resultto be in the range [-180, 180].
269   *
270   * @param time  The time at which the moon's age is desired,
271   *              in millis since 1/1/1970.
272   */
273  static double moonAge(UDate time, UErrorCode &status);
274
275  //-------------------------------------------------------------------------
276  // Internal data....
277  //
278
279  /**
280   * <code>CIVIL</code> if this object uses the fixed-cycle Islamic civil calendar,
281   * and <code>ASTRONOMICAL</code> if it approximates the true religious calendar using
282   * astronomical calculations for the time of the new moon.
283   */
284  ECalculationType cType;
285
286  //----------------------------------------------------------------------
287  // Calendar framework
288  //----------------------------------------------------------------------
289 protected:
290  /**
291   * @internal
292   */
293  virtual int32_t handleGetLimit(UCalendarDateFields field, ELimitType limitType) const;
294
295  /**
296   * Return the length (in days) of the given month.
297   *
298   * @param year  The hijri year
299   * @param year  The hijri month, 0-based
300   * @internal
301   */
302  virtual int32_t handleGetMonthLength(int32_t extendedYear, int32_t month) const;
303
304  /**
305   * Return the number of days in the given Islamic year
306   * @internal
307   */
308  virtual int32_t handleGetYearLength(int32_t extendedYear) const;
309
310  //-------------------------------------------------------------------------
311  // Functions for converting from field values to milliseconds....
312  //-------------------------------------------------------------------------
313
314  // Return JD of start of given month/year
315  /**
316   * @internal
317   */
318  virtual int32_t handleComputeMonthStart(int32_t eyear, int32_t month, UBool useMonth) const;
319
320  //-------------------------------------------------------------------------
321  // Functions for converting from milliseconds to field values
322  //-------------------------------------------------------------------------
323
324  /**
325   * @internal
326   */
327  virtual int32_t handleGetExtendedYear();
328
329  /**
330   * Override Calendar to compute several fields specific to the Islamic
331   * calendar system.  These are:
332   *
333   * <ul><li>ERA
334   * <li>YEAR
335   * <li>MONTH
336   * <li>DAY_OF_MONTH
337   * <li>DAY_OF_YEAR
338   * <li>EXTENDED_YEAR</ul>
339   *
340   * The DAY_OF_WEEK and DOW_LOCAL fields are already set when this
341   * method is called. The getGregorianXxx() methods return Gregorian
342   * calendar equivalents for the given Julian day.
343   * @internal
344   */
345  virtual void handleComputeFields(int32_t julianDay, UErrorCode &status);
346
347  // UObject stuff
348 public:
349  /**
350   * @return   The class ID for this object. All objects of a given class have the
351   *           same class ID. Objects of other classes have different class IDs.
352   * @internal
353   */
354  virtual UClassID getDynamicClassID(void) const;
355
356  /**
357   * Return the class ID for this class. This is useful only for comparing to a return
358   * value from getDynamicClassID(). For example:
359   *
360   *      Base* polymorphic_pointer = createPolymorphicObject();
361   *      if (polymorphic_pointer->getDynamicClassID() ==
362   *          Derived::getStaticClassID()) ...
363   *
364   * @return   The class ID for all objects of this class.
365   * @internal
366   */
367  /*U_I18N_API*/ static UClassID U_EXPORT2 getStaticClassID(void);
368
369  /**
370   * return the calendar type, "buddhist".
371   *
372   * @return calendar type
373   * @internal
374   */
375  virtual const char * getType() const;
376
377 private:
378  IslamicCalendar(); // default constructor not implemented
379
380  // Default century.
381 protected:
382
383  /**
384   * (Overrides Calendar) Return true if the current date for this Calendar is in
385   * Daylight Savings Time. Recognizes DST_OFFSET, if it is set.
386   *
387   * @param status Fill-in parameter which receives the status of this operation.
388   * @return   True if the current date for this Calendar is in Daylight Savings Time,
389   *           false, otherwise.
390   * @internal
391   */
392  virtual UBool inDaylightTime(UErrorCode& status) const;
393
394
395  /**
396   * Returns TRUE because the Islamic Calendar does have a default century
397   * @internal
398   */
399  virtual UBool haveDefaultCentury() const;
400
401  /**
402   * Returns the date of the start of the default century
403   * @return start of century - in milliseconds since epoch, 1970
404   * @internal
405   */
406  virtual UDate defaultCenturyStart() const;
407
408  /**
409   * Returns the year in which the default century begins
410   * @internal
411   */
412  virtual int32_t defaultCenturyStartYear() const;
413
414 private:
415  /**
416   * Initializes the 100-year window that dates with 2-digit years
417   * are considered to fall within so that its start date is 80 years
418   * before the current time.
419   */
420  static void  initializeSystemDefaultCentury(void);
421};
422
423U_NAMESPACE_END
424
425#endif
426#endif
427
428
429
430