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_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_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(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