1/* Copyright (c) 2002,2003 CrystalClear Software, Inc.
2 * Use, modification and distribution is subject to the
3 * Boost Software License, Version 1.0. (See accompanying
4 * file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
5 * Author: Jeff Garland, Bart Garst
6 * $Date$
7 */
8
9#ifndef NO_BOOST_DATE_TIME_INLINE
10 #undef BOOST_DATE_TIME_INLINE
11 #define BOOST_DATE_TIME_INLINE inline
12#endif
13
14namespace boost {
15namespace date_time {
16 //! Return the day of the week (0==Sunday, 1==Monday, etc)
17 /*! Converts a year-month-day into a day of the week number
18 */
19 template<typename ymd_type_, typename date_int_type_>
20 BOOST_DATE_TIME_INLINE
21 unsigned short
22 gregorian_calendar_base<ymd_type_,date_int_type_>::day_of_week(const ymd_type& ymd) {
23 unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
24 unsigned short y = static_cast<unsigned short>(ymd.year - a);
25 unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 2);
26 unsigned short d = static_cast<unsigned short>((ymd.day + y + (y/4) - (y/100) + (y/400) + (31*m)/12) % 7);
27 //std::cout << year << "-" << month << "-" << day << " is day: " << d << "\n";
28 return d;
29 }
30
31 //!Return the iso week number for the date
32 /*!Implements the rules associated with the iso 8601 week number.
33 Basically the rule is that Week 1 of the year is the week that contains
34 January 4th or the week that contains the first Thursday in January.
35 Reference for this algorithm is the Calendar FAQ by Claus Tondering, April 2000.
36 */
37 template<typename ymd_type_, typename date_int_type_>
38 BOOST_DATE_TIME_INLINE
39 int
40 gregorian_calendar_base<ymd_type_,date_int_type_>::week_number(const ymd_type& ymd) {
41 unsigned long julianbegin = julian_day_number(ymd: ymd_type(ymd.year,1,1));
42 unsigned long juliantoday = julian_day_number(ymd);
43 unsigned long day = (julianbegin + 3) % 7;
44 unsigned long week = (juliantoday + day - julianbegin + 4)/7;
45
46 if ((week >= 1) && (week <= 52)) {
47 return static_cast<int>(week);
48 }
49
50 if (week == 53) {
51 if((day==6) ||(day == 5 && is_leap_year(ymd.year))) {
52 return static_cast<int>(week); //under these circumstances week == 53.
53 } else {
54 return 1; //monday - wednesday is in week 1 of next year
55 }
56 }
57 //if the week is not in current year recalculate using the previous year as the beginning year
58 else if (week == 0) {
59 julianbegin = julian_day_number(ymd: ymd_type(static_cast<unsigned short>(ymd.year-1),1,1));
60 juliantoday = julian_day_number(ymd);
61 day = (julianbegin + 3) % 7;
62 week = (juliantoday + day - julianbegin + 4)/7;
63 return static_cast<int>(week);
64 }
65
66 return static_cast<int>(week); //not reachable -- well except if day == 5 and is_leap_year != true
67
68 }
69
70 //! Convert a ymd_type into a day number
71 /*! The day number is an absolute number of days since the start of count
72 */
73 template<typename ymd_type_, typename date_int_type_>
74 BOOST_DATE_TIME_INLINE
75 date_int_type_
76 gregorian_calendar_base<ymd_type_,date_int_type_>::day_number(const ymd_type& ymd)
77 {
78 unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
79 unsigned short y = static_cast<unsigned short>(ymd.year + 4800 - a);
80 unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 3);
81 unsigned long d = ymd.day + ((153*m + 2)/5) + 365*y + (y/4) - (y/100) + (y/400) - 32045;
82 return static_cast<date_int_type>(d);
83 }
84
85 //! Convert a year-month-day into the julian day number
86 /*! Since this implementation uses julian day internally, this is the same as the day_number.
87 */
88 template<typename ymd_type_, typename date_int_type_>
89 BOOST_DATE_TIME_INLINE
90 date_int_type_
91 gregorian_calendar_base<ymd_type_,date_int_type_>::julian_day_number(const ymd_type& ymd)
92 {
93 return day_number(ymd);
94 }
95
96 //! Convert year-month-day into a modified julian day number
97 /*! The day number is an absolute number of days.
98 * MJD 0 thus started on 17 Nov 1858(Gregorian) at 00:00:00 UTC
99 */
100 template<typename ymd_type_, typename date_int_type_>
101 BOOST_DATE_TIME_INLINE
102 date_int_type_
103 gregorian_calendar_base<ymd_type_,date_int_type_>::modjulian_day_number(const ymd_type& ymd)
104 {
105 return julian_day_number(ymd)-2400001; //prerounded
106 }
107
108 //! Change a day number into a year-month-day
109 template<typename ymd_type_, typename date_int_type_>
110 BOOST_DATE_TIME_INLINE
111 ymd_type_
112 gregorian_calendar_base<ymd_type_,date_int_type_>::from_day_number(date_int_type dayNumber)
113 {
114 date_int_type a = dayNumber + 32044;
115 date_int_type b = (4*a + 3)/146097;
116 date_int_type c = a-((146097*b)/4);
117 date_int_type d = (4*c + 3)/1461;
118 date_int_type e = c - (1461*d)/4;
119 date_int_type m = (5*e + 2)/153;
120 unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
121 unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
122 year_type year = static_cast<unsigned short>(100*b + d - 4800 + (m/10));
123 //std::cout << year << "-" << month << "-" << day << "\n";
124
125 return ymd_type(static_cast<unsigned short>(year),month,day);
126 }
127
128 //! Change a day number into a year-month-day
129 template<typename ymd_type_, typename date_int_type_>
130 BOOST_DATE_TIME_INLINE
131 ymd_type_
132 gregorian_calendar_base<ymd_type_,date_int_type_>::from_julian_day_number(date_int_type dayNumber)
133 {
134 date_int_type a = dayNumber + 32044;
135 date_int_type b = (4*a+3)/146097;
136 date_int_type c = a - ((146097*b)/4);
137 date_int_type d = (4*c + 3)/1461;
138 date_int_type e = c - ((1461*d)/4);
139 date_int_type m = (5*e + 2)/153;
140 unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
141 unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
142 year_type year = static_cast<year_type>(100*b + d - 4800 + (m/10));
143 //std::cout << year << "-" << month << "-" << day << "\n";
144
145 return ymd_type(year,month,day);
146 }
147
148 //! Change a modified julian day number into a year-month-day
149 template<typename ymd_type_, typename date_int_type_>
150 BOOST_DATE_TIME_INLINE
151 ymd_type_
152 gregorian_calendar_base<ymd_type_,date_int_type_>::from_modjulian_day_number(date_int_type dayNumber) {
153 date_int_type jd = dayNumber + 2400001; //is 2400000.5 prerounded
154 return from_julian_day_number(dayNumber: jd);
155 }
156
157 //! Determine if the provided year is a leap year
158 /*!
159 *@return true if year is a leap year, false otherwise
160 */
161 template<typename ymd_type_, typename date_int_type_>
162 BOOST_DATE_TIME_INLINE
163 bool
164 gregorian_calendar_base<ymd_type_,date_int_type_>::is_leap_year(year_type year)
165 {
166 //divisible by 4, not if divisible by 100, but true if divisible by 400
167 return (!(year % 4)) && ((year % 100) || (!(year % 400)));
168 }
169
170 //! Calculate the last day of the month
171 /*! Find the day which is the end of the month given year and month
172 * No error checking is performed.
173 */
174 template<typename ymd_type_, typename date_int_type_>
175 BOOST_DATE_TIME_INLINE
176 unsigned short
177 gregorian_calendar_base<ymd_type_,date_int_type_>::end_of_month_day(year_type year,
178 month_type month)
179 {
180 switch (month) {
181 case 2:
182 if (is_leap_year(year)) {
183 return 29;
184 } else {
185 return 28;
186 };
187 case 4:
188 case 6:
189 case 9:
190 case 11:
191 return 30;
192 default:
193 return 31;
194 };
195
196 }
197
198 //! Provide the ymd_type specification for the calandar start
199 template<typename ymd_type_, typename date_int_type_>
200 BOOST_DATE_TIME_INLINE
201 ymd_type_
202 gregorian_calendar_base<ymd_type_,date_int_type_>::epoch()
203 {
204 return ymd_type(1400,1,1);
205 }
206
207 //! Defines length of a week for week calculations
208 template<typename ymd_type_, typename date_int_type_>
209 BOOST_DATE_TIME_INLINE
210 unsigned short
211 gregorian_calendar_base<ymd_type_,date_int_type_>::days_in_week()
212 {
213 return 7;
214 }
215
216
217} } //namespace gregorian
218
219
220

source code of boost/boost/date_time/gregorian_calendar.ipp