plugins/fn-hebrew-date/hdate_hdate.c

   1 /*
   2  * hdate_hdate.c: convert georgean and hebrew calendars.
   3  *
   4  * Author:
   5  *   Yaacov Zamir <kzamir@walla.co.il>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see <https://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <gnumeric-config.h>
  22 #include <gnumeric.h>
  23
  24 #include "hdate.h"
  25
  26 /* constants, in 1/18th of minute */
  27 #define HOUR 1080
  28 #define DAY  (24*HOUR)
  29 #define WEEK (7*DAY)
  30 #define M(h,p) ((h)*HOUR+p)
  31 #define MONTH (DAY+M(12,793))
  32
  33 /**
  34  @brief Return the days from the start
  35
  36  @param y The years
  37  @warning internal function.
  38 */
  39 int
  40 hdate_days_from_start (int y)
  41 {
  42         int m, nm, dw, s, l;
  43
  44         l = y * 7 + 1;          /* no. of leap months */
  45         m = y * 12 + l / 19;    /* total no. of months */
  46         l %= 19;
  47         nm = m * MONTH + M (1 + 6, 779);        /* molad new year 3744 (16BC) + 6 hours */
  48         s = m * 28 + nm / DAY - 2;
  49
  50         nm %= WEEK;
  51         dw = nm / DAY;
  52         nm %= DAY;
  53
  54         /* special cases of Molad Zaken */
  55         if ((l < 12 && dw == 3 && nm >= M (9 + 6, 204)) ||
  56             (l < 7 && dw == 2 && nm >= M (15 + 6, 589)))
  57                 s++, dw++;
  58         /* ADU */
  59         if (dw == 1 || dw == 4 || dw == 6)
  60                 s++;
  61         return s;
  62 }
  63
  64 /**
  65  @brief compute hebrew date from gregorian date
  66
  67  @param d Day of month 1..31
  68  @param m Month 1..12 ,  if m or d is 0 return current date.
  69  @param y Year in 4 digits e.g. 2001
  70  */
  71 int
  72 hdate_gdate_to_hdate (int d, int m, int y, int *hd, int *hm, int *hy)
  73 {
  74         int jd;
  75
  76         /* sanity checks */
  77         if (!(m >= 1 && m <= 12) ||
  78             !((d >= 1)
  79               && ((y >= 3000 && m == 6 && d <= 59)
  80                   || (d <= 31))) || !(y > 0))
  81                 return 1;
  82
  83         /* end of cheking */
  84
  85         jd = hdate_gdate_to_jd (d, m, y);
  86
  87         hdate_jd_to_hdate (jd, hd, hm, hy);
  88
  89         return 0;
  90
  91 }
  92
  93 /**
  94  @brief compute general date structure from hebrew date
  95
  96  @param d Day of month 1..31
  97  @param m Month 0..13 ,  if m or d is 0 return current date.
  98  @param y Year in 4 digits e.g. 5731
  99
 100  @attention no sanity cheak !!
 101  */
 102 int
 103 hdate_hdate_to_gdate (int d, int m, int y, int *gd, int *gm, int *gy)
 104 {
 105         int jd;
 106
 107         /* sanity checks */
 108         if (!(m >= 1 && m <= 12) ||
 109             !((d >= 1)
 110               && ((y >= 3000 && m == 6 && d <= 59)
 111                   || (d <= 31))) || !(y > 0))
 112                 return 1;
 113
 114         /* end of cheking */
 115
 116         jd = hdate_hdate_to_jd (d, m, y);
 117
 118         hdate_jd_to_gdate (jd, gd, gm, gy);
 119
 120         return 0;
 121 }
 122
 123 /**
 124  @brief Compute Julian day (jd from Gregorian day, month and year (d, m, y)
 125  Algorithm from 'Julian and Gregorian Day Numbers' by Peter Meyer
 126  @author Yaacov Zamir ( algorithm from Henry F. Fliegel and Thomas C. Van Flandern ,1968)
 127
 128  @param d Day of month 1..31
 129  @param m Month 1..12
 130  @param y Year in 4 digits e.g. 2001
 131  */
 132 int
 133 hdate_gdate_to_jd (int d, int m, int y)
 134 {
 135         int jd;
 136
 137         jd = (1461 * (y + 4800 + (m - 14) / 12)) / 4 +
 138                 (367 * (m - 2 - 12 * ((m - 14) / 12))) / 12 -
 139                 (3 * ((y + 4900 + (m - 14) / 12) / 100)) / 4 + d - 32075;
 140
 141         return jd;
 142 }
 143
 144 /**
 145  @brief Converting from the Julian day to the Gregorian day
 146  Algorithm from 'Julian and Gregorian Day Numbers' by Peter Meyer
 147  @author Yaacov Zamir ( Algorithm, Henry F. Fliegel and Thomas C. Van Flandern ,1968)
 148
 149  @param jd Julian day
 150  @param d Return Day of month 1..31
 151  @param m Return Month 1..12
 152  @param y Return Year in 4 digits e.g. 2001
 153  */
 154 void
 155 hdate_jd_to_gdate (int jd, int *d, int *m, int *y)
 156 {
 157         int l, n, i, j;
 158
 159         l = jd + 68569;
 160         n = (4 * l) / 146097;
 161         l = l - (146097 * n + 3) / 4;
 162         i = (4000 * (l + 1)) / 1461001; /* that's 1,461,001 */
 163         l = l - (1461 * i) / 4 + 31;
 164         j = (80 * l) / 2447;
 165         *d = l - (2447 * j) / 80;
 166         l = j / 11;
 167         *m = j + 2 - (12 * l);
 168         *y = 100 * (n - 49) + i + l;    /* that's a lower-case L */
 169 }
 170
 171 /**
 172  @brief Converting from the Julian day to the Hebrew day
 173  @author Amos Shapir 1984 (rev. 1985, 1992) Yaacov Zamir 2003-2005
 174
 175  @param jd Julian day
 176  @param d Return Day of month 1..31
 177  @param m Return Month 1..14
 178  @param y Return Year in 4 digits e.g. 2001
 179  */
 180 void
 181 hdate_jd_to_hdate (int jd, int *d, int *m, int *y)
 182 {
 183         int s;
 184         int l, n, i, j;
 185
 186         l = jd + 68569;
 187         n = (4 * l) / 146097;
 188         l = l - (146097 * n + 3) / 4;
 189         i = (4000 * (l + 1)) / 1461001; /* that's 1,461,001 */
 190         l = l - (1461 * i) / 4 + 31;
 191         j = (80 * l) / 2447;
 192         l = j / 11;
 193         *y = 100 * (n - 49) + i + l;    /* that's a lower-case L */
 194
 195         *d = jd - 1715119;      /* julean to days since 1 Tishrei 3744 */
 196
 197         *y += 16;
 198         s = hdate_days_from_start (*y);
 199         *m = hdate_days_from_start (*y + 1);
 200
 201         while (*d >= *m)
 202         {                       /* computed year was underestimated */
 203                 s = *m;
 204                 (*y)++;
 205                 *m = hdate_days_from_start (*y + 1);
 206         }
 207         *d -= s;
 208         s = *m - s;             /* size of current year */
 209         *y += 3744;
 210
 211         /* compute day and month */
 212         if (*d >= s - 236)
 213         {                       /* last 8 months are regular */
 214                 *d -= s - 236;
 215                 *m = *d * 2 / 59;
 216                 *d -= (*m * 59 + 1) / 2;
 217                 *m += 4;
 218                 if (s > 365 && *m <= 5) /* Adar of Meuberet */
 219                         *m += 8;
 220         }
 221         else
 222         {
 223                 /* first 4 months have 117-119 days */
 224                 s = 114 + s % 10;
 225                 *m = *d * 4 / s;
 226                 *d -= (*m * s + 3) / 4;
 227         }
 228 }
 229
 230 /**
 231  @brief Compute Julian day (jd from Hebrew day, month and year (d, m, y)
 232  @author Amos Shapir 1984 (rev. 1985, 1992) Yaacov Zamir 2003-2005
 233
 234  @param d Day of month 1..31
 235  @param m Month 1..14
 236  @param y Year in 4 digits e.g. 5753
 237  */
 238 int
 239 hdate_hdate_to_jd (int d, int m, int y)
 240 {
 241         int s;
 242
 243         y -= 3744;
 244         s = hdate_days_from_start (y);
 245         d += s;
 246         s = hdate_days_from_start (y + 1) - s;  /* length of year */
 247
 248         if (m == 13)
 249         {
 250                 m = 6;
 251         }
 252         if (m == 14)
 253         {
 254                 m = 6;
 255                 d += 30;
 256         }
 257
 258         d += (59 * (m - 1) + 1) / 2;    /* regular months */
 259         /* special cases */
 260         if (s % 10 > 4 && m > 2)        /* long Heshvan */
 261                 d++;
 262         if (s % 10 < 4 && m > 3)        /* short Kislev */
 263                 d--;
 264
 265         if (s > 365 && m > 6)   /* leap year */
 266                 d += 30;
 267         d -= 6002;
 268
 269         y = (d + 36525) * 4 / 146097 - 1;
 270         d -= y / 4 * 146097 + (y % 4) * 36524;
 271
 272         d += 1715119;           /* days since 1 Tishrei 3744 to julean */
 273
 274         return d;
 275 }