//----------------------------------------------------------------------------- // Copyright © 2004 - Philip Howard - All rights reserved // // This program is free software; you can redistribute it and/or // modify it under the terms of the GNU General Public License // as published by the Free Software Foundation; either version 2 // of the License, or (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program; if not, write to the Free Software // Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. //----------------------------------------------------------------------------- // package libh/time // homepage http://libh.slashusr.org/ //----------------------------------------------------------------------------- // author Philip Howard // email libh at ipal dot org // homepage http://phil.ipal.org/ //----------------------------------------------------------------------------- // This file is best viewed using a fixed spaced font such as Courier // and in a display at least 120 columns wide. //----------------------------------------------------------------------------- // reference Explanatory Supplement to the Astronomical Almanac, // P. Kenneth Seidelmann, editor [ISBN 0-935702-68-7] // http://shop.bn.com/bookSearch/isbnInquiry.asp?isbn=0935702687 //----------------------------------------------------------------------------- #include #include "time_lib.h" __PROTO_BEGIN__ //----------------------------------------------------------------------------- // function ymd_gregorian_to_eday // // purpose Convert a Gregorian calendar date to an Earth Day value. // // arguments 1 (long) Gregorian calendar year (0 = 1 BC, 1 = 1 AD) // 2 (int) Gregorian calendar month (1-12) // 3 (int) Gregorian calendar date (1-31) // // returns (eday_t) resultant Earth Day value // // note The calculation is for the proleptic Gregorian calendar. // There is no accomodation for selection between Gregorian // and Julian calendars. Since different areas of the world // switched calendars at different dates, the calling program // will have to determine on its own what is the appropriate // calendar context and call ymd_gregorian_to_eday() or ymd_julian_to_eday(). //----------------------------------------------------------------------------- eday_t ymd_gregorian_to_eday ( long arg_year , int arg_month , int arg_date ) __PROTO_END__ { //-------------------------------------------------------------- // Define a lookup table indexed by the year in a 400 year cycle // yielding the number of days in the cycle to that year. //-------------------------------------------------------------- static int year_to_day[400] = { 0, 366, 731, 1096, 1461, 1827, 2192, 2557, 2922, 3288, 3653, 4018, 4383, 4749, 5114, 5479, 5844, 6210, 6575, 6940, 7305, 7671, 8036, 8401, 8766, 9132, 9497, 9862, 10227, 10593, 10958, 11323, 11688, 12054, 12419, 12784, 13149, 13515, 13880, 14245, 14610, 14976, 15341, 15706, 16071, 16437, 16802, 17167, 17532, 17898, 18263, 18628, 18993, 19359, 19724, 20089, 20454, 20820, 21185, 21550, 21915, 22281, 22646, 23011, 23376, 23742, 24107, 24472, 24837, 25203, 25568, 25933, 26298, 26664, 27029, 27394, 27759, 28125, 28490, 28855, 29220, 29586, 29951, 30316, 30681, 31047, 31412, 31777, 32142, 32508, 32873, 33238, 33603, 33969, 34334, 34699, 35064, 35430, 35795, 36160, 36525, 36890, 37255, 37620, 37985, 38351, 38716, 39081, 39446, 39812, 40177, 40542, 40907, 41273, 41638, 42003, 42368, 42734, 43099, 43464, 43829, 44195, 44560, 44925, 45290, 45656, 46021, 46386, 46751, 47117, 47482, 47847, 48212, 48578, 48943, 49308, 49673, 50039, 50404, 50769, 51134, 51500, 51865, 52230, 52595, 52961, 53326, 53691, 54056, 54422, 54787, 55152, 55517, 55883, 56248, 56613, 56978, 57344, 57709, 58074, 58439, 58805, 59170, 59535, 59900, 60266, 60631, 60996, 61361, 61727, 62092, 62457, 62822, 63188, 63553, 63918, 64283, 64649, 65014, 65379, 65744, 66110, 66475, 66840, 67205, 67571, 67936, 68301, 68666, 69032, 69397, 69762, 70127, 70493, 70858, 71223, 71588, 71954, 72319, 72684, 73049, 73414, 73779, 74144, 74509, 74875, 75240, 75605, 75970, 76336, 76701, 77066, 77431, 77797, 78162, 78527, 78892, 79258, 79623, 79988, 80353, 80719, 81084, 81449, 81814, 82180, 82545, 82910, 83275, 83641, 84006, 84371, 84736, 85102, 85467, 85832, 86197, 86563, 86928, 87293, 87658, 88024, 88389, 88754, 89119, 89485, 89850, 90215, 90580, 90946, 91311, 91676, 92041, 92407, 92772, 93137, 93502, 93868, 94233, 94598, 94963, 95329, 95694, 96059, 96424, 96790, 97155, 97520, 97885, 98251, 98616, 98981, 99346, 99712,100077,100442,100807,101173,101538,101903, 102268,102634,102999,103364,103729,104095,104460,104825,105190,105556, 105921,106286,106651,107017,107382,107747,108112,108478,108843,109208, 109573,109938,110303,110668,111033,111399,111764,112129,112494,112860, 113225,113590,113955,114321,114686,115051,115416,115782,116147,116512, 116877,117243,117608,117973,118338,118704,119069,119434,119799,120165, 120530,120895,121260,121626,121991,122356,122721,123087,123452,123817, 124182,124548,124913,125278,125643,126009,126374,126739,127104,127470, 127835,128200,128565,128931,129296,129661,130026,130392,130757,131122, 131487,131853,132218,132583,132948,133314,133679,134044,134409,134775, 135140,135505,135870,136236,136601,136966,137331,137697,138062,138427, 138792,139158,139523,139888,140253,140619,140984,141349,141714,142080, 142445,142810,143175,143541,143906,144271,144636,145002,145367,145732 }; //---------------------------------------------------------- // Define a lookup table indexed by the year offset in a 400 // year cycle yielding an indicator if this is a leap year. //---------------------------------------------------------- static char year_is_leapyear[400] = { 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0, 1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0 }; //----------------------------------------------------- // Define a lookup table indexed by the month offset in // a year yielding the number of days to that month. //----------------------------------------------------- static int month_to_day[12] = { 0,31,59,90,120,151,181,212,243,273,304,334 }; //----------------------------------------------------- // Define a lookup table indexed by the month offset in // a year yielding the number of days in that month. //----------------------------------------------------- static int days_in_month[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 }; //------------------------ // Define other variables. //------------------------ long cycle ; long days ; int year ; int month ; int leapyear ; //----------------------------------------------------------- // Split year into cycle number and year offset within cycle. //----------------------------------------------------------- cycle = quo_ni( arg_year, 400 ); year = arg_year - cycle * 400; leapyear = year_is_leapyear[ year ]; //------------------------------ // Get month into range 0 to 11. //------------------------------ month = arg_month - 1; if ( arg_month < 1 ) month = 0; else if ( arg_month > 12 ) month = 11; //------------------------------------ // Get days into range for this month. //------------------------------------ days = days_in_month[ month ] + ( leapyear && month == 1 ); if ( arg_date < 1 ) days = 1; else if ( arg_date < days ) days = arg_date; -- days; //-------------------------------- // Add days in year to this month. //-------------------------------- days += month_to_day[ month ]; if ( leapyear && month > 1 ) ++ days; //-------------------------------------------------------- // Add days in cycle to this year, days to cycle from year // zero, adjust to epoch, and return this number of days. //-------------------------------------------------------- return days + year_to_day[ year ] + cycle * 146097 + EDAY_1_JAN_0; }