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
10namespace boost {
11namespace date_time {
12 //! Return the day of the week (0==Sunday, 1==Monday, etc)
13 /*! Converts a year-month-day into a day of the week number
14 */
15 template<typename ymd_type_, typename date_int_type_>
16 BOOST_CXX14_CONSTEXPR
17 inline
18 unsigned short
19 gregorian_calendar_base<ymd_type_,date_int_type_>::day_of_week(const ymd_type& ymd) {
20 unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
21 unsigned short y = static_cast<unsigned short>(ymd.year - a);
22 unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 2);
23 unsigned short d = static_cast<unsigned short>((ymd.day + y + (y/4) - (y/100) + (y/400) + (31*m)/12) % 7);
24 //std::cout << year << "-" << month << "-" << day << " is day: " << d << "\n";
25 return d;
26 }
27
28 //!Return the iso week number for the date
29 /*!Implements the rules associated with the iso 8601 week number.
30 Basically the rule is that Week 1 of the year is the week that contains
31 January 4th or the week that contains the first Thursday in January.
32 Reference for this algorithm is the Calendar FAQ by Claus Tondering, April 2000.
33 */
34 template<typename ymd_type_, typename date_int_type_>
35 BOOST_CXX14_CONSTEXPR
36 inline
37 int
38 gregorian_calendar_base<ymd_type_,date_int_type_>::week_number(const ymd_type& ymd) {
39 unsigned long julianbegin = julian_day_number(ymd: ymd_type(ymd.year,1,1));
40 unsigned long juliantoday = julian_day_number(ymd);
41 unsigned long day = (julianbegin + 3) % 7;
42 unsigned long week = (juliantoday + day - julianbegin + 4)/7;
43
44 if ((week >= 1) && (week <= 52)) {
45 return static_cast<int>(week);
46 }
47
48 if (week == 53) {
49 if((day==6) ||(day == 5 && is_leap_year(ymd.year))) {
50 return static_cast<int>(week); //under these circumstances week == 53.
51 } else {
52 return 1; //monday - wednesday is in week 1 of next year
53 }
54 }
55 //if the week is not in current year recalculate using the previous year as the beginning year
56 else if (week == 0) {
57 julianbegin = julian_day_number(ymd: ymd_type(static_cast<unsigned short>(ymd.year-1),1,1));
58 juliantoday = julian_day_number(ymd);
59 day = (julianbegin + 3) % 7;
60 week = (juliantoday + day - julianbegin + 4)/7;
61 return static_cast<int>(week);
62 }
63
64 return static_cast<int>(week); //not reachable -- well except if day == 5 and is_leap_year != true
65
66 }
67
68 //! Convert a ymd_type into a day number
69 /*! The day number is an absolute number of days since the start of count
70 */
71 template<typename ymd_type_, typename date_int_type_>
72 BOOST_CXX14_CONSTEXPR
73 inline
74 date_int_type_
75 gregorian_calendar_base<ymd_type_,date_int_type_>::day_number(const ymd_type& ymd)
76 {
77 unsigned short a = static_cast<unsigned short>((14-ymd.month)/12);
78 unsigned short y = static_cast<unsigned short>(ymd.year + 4800 - a);
79 unsigned short m = static_cast<unsigned short>(ymd.month + 12*a - 3);
80 unsigned long d = ymd.day + ((153*m + 2)/5) + 365*y + (y/4) - (y/100) + (y/400) - 32045;
81 return static_cast<date_int_type>(d);
82 }
83
84 //! Convert a year-month-day into the julian day number
85 /*! Since this implementation uses julian day internally, this is the same as the day_number.
86 */
87 template<typename ymd_type_, typename date_int_type_>
88 BOOST_CXX14_CONSTEXPR
89 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_CXX14_CONSTEXPR
102 inline
103 date_int_type_
104 gregorian_calendar_base<ymd_type_,date_int_type_>::modjulian_day_number(const ymd_type& ymd)
105 {
106 return julian_day_number(ymd)-2400001; //prerounded
107 }
108
109 //! Change a day number into a year-month-day
110 template<typename ymd_type_, typename date_int_type_>
111 BOOST_CXX14_CONSTEXPR
112 inline
113 ymd_type_
114 gregorian_calendar_base<ymd_type_,date_int_type_>::from_day_number(date_int_type dayNumber)
115 {
116 date_int_type a = dayNumber + 32044;
117 date_int_type b = (4*a + 3)/146097;
118 date_int_type c = a-((146097*b)/4);
119 date_int_type d = (4*c + 3)/1461;
120 date_int_type e = c - (1461*d)/4;
121 date_int_type m = (5*e + 2)/153;
122 unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
123 unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
124 year_type year = static_cast<unsigned short>(100*b + d - 4800 + (m/10));
125 //std::cout << year << "-" << month << "-" << day << "\n";
126
127 return ymd_type(static_cast<unsigned short>(year),month,day);
128 }
129
130 //! Change a day number into a year-month-day
131 template<typename ymd_type_, typename date_int_type_>
132 BOOST_CXX14_CONSTEXPR
133 inline
134 ymd_type_
135 gregorian_calendar_base<ymd_type_,date_int_type_>::from_julian_day_number(date_int_type dayNumber)
136 {
137 date_int_type a = dayNumber + 32044;
138 date_int_type b = (4*a+3)/146097;
139 date_int_type c = a - ((146097*b)/4);
140 date_int_type d = (4*c + 3)/1461;
141 date_int_type e = c - ((1461*d)/4);
142 date_int_type m = (5*e + 2)/153;
143 unsigned short day = static_cast<unsigned short>(e - ((153*m + 2)/5) + 1);
144 unsigned short month = static_cast<unsigned short>(m + 3 - 12 * (m/10));
145 year_type year = static_cast<year_type>(100*b + d - 4800 + (m/10));
146 //std::cout << year << "-" << month << "-" << day << "\n";
147
148 return ymd_type(year,month,day);
149 }
150
151 //! Change a modified julian day number into a year-month-day
152 template<typename ymd_type_, typename date_int_type_>
153 BOOST_CXX14_CONSTEXPR
154 inline
155 ymd_type_
156 gregorian_calendar_base<ymd_type_,date_int_type_>::from_modjulian_day_number(date_int_type dayNumber) {
157 date_int_type jd = dayNumber + 2400001; //is 2400000.5 prerounded
158 return from_julian_day_number(dayNumber: jd);
159 }
160
161 //! Determine if the provided year is a leap year
162 /*!
163 *@return true if year is a leap year, false otherwise
164 */
165 template<typename ymd_type_, typename date_int_type_>
166 BOOST_CXX14_CONSTEXPR
167 inline
168 bool
169 gregorian_calendar_base<ymd_type_,date_int_type_>::is_leap_year(year_type year)
170 {
171 //divisible by 4, not if divisible by 100, but true if divisible by 400
172 return (!(year % 4)) && ((year % 100) || (!(year % 400)));
173 }
174
175 //! Calculate the last day of the month
176 /*! Find the day which is the end of the month given year and month
177 * No error checking is performed.
178 */
179 template<typename ymd_type_, typename date_int_type_>
180 BOOST_CXX14_CONSTEXPR
181 inline
182 unsigned short
183 gregorian_calendar_base<ymd_type_,date_int_type_>::end_of_month_day(year_type year,
184 month_type month)
185 {
186 switch (month) {
187 case 2:
188 if (is_leap_year(year)) {
189 return 29;
190 } else {
191 return 28;
192 }
193 case 4:
194 case 6:
195 case 9:
196 case 11:
197 return 30;
198 default:
199 return 31;
200 }
201 }
202
203 //! Provide the ymd_type specification for the calendar start
204 template<typename ymd_type_, typename date_int_type_>
205 BOOST_CXX14_CONSTEXPR
206 inline
207 ymd_type_
208 gregorian_calendar_base<ymd_type_,date_int_type_>::epoch()
209 {
210 return ymd_type(1400,1,1);
211 }
212
213 //! Defines length of a week for week calculations
214 template<typename ymd_type_, typename date_int_type_>
215 BOOST_CXX14_CONSTEXPR
216 inline
217 unsigned short
218 gregorian_calendar_base<ymd_type_,date_int_type_>::days_in_week()
219 {
220 return 7;
221 }
222
223
224} } //namespace gregorian
225

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