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Diffstat (limited to 'ext/calendar/julian.c')
| -rw-r--r-- | ext/calendar/julian.c | 240 |
1 files changed, 0 insertions, 240 deletions
diff --git a/ext/calendar/julian.c b/ext/calendar/julian.c deleted file mode 100644 index 094b4ed647..0000000000 --- a/ext/calendar/julian.c +++ /dev/null @@ -1,240 +0,0 @@ -/* $selId: julian.c,v 2.0 1995/10/24 01:13:06 lees Exp $ - * Copyright 1993-1995, Scott E. Lee, all rights reserved. - * Permission granted to use, copy, modify, distribute and sell so long as - * the above copyright and this permission statement are retained in all - * copies. THERE IS NO WARRANTY - USE AT YOUR OWN RISK. - */ - -/************************************************************************** - * - * These are the externally visible components of this file: - * - * void - * SdnToJulian( - * long int sdn, - * int *pYear, - * int *pMonth, - * int *pDay); - * - * Convert a SDN to a Julian calendar date. If the input SDN is less than - * 1, the three output values will all be set to zero, otherwise *pYear - * will be >= -4713 and != 0; *pMonth will be in the range 1 to 12 - * inclusive; *pDay will be in the range 1 to 31 inclusive. - * - * long int - * JulianToSdn( - * int inputYear, - * int inputMonth, - * int inputDay); - * - * Convert a Julian calendar date to a SDN. Zero is returned when the - * input date is detected as invalid or out of the supported range. The - * return value will be > 0 for all valid, supported dates, but there are - * some invalid dates that will return a positive value. To verify that a - * date is valid, convert it to SDN and then back and compare with the - * original. - * - * VALID RANGE - * - * 4713 B.C. to at least 10000 A.D. - * - * Although this software can handle dates all the way back to 4713 - * B.C., such use may not be meaningful. The calendar was created in - * 46 B.C., but the details did not stabilize until at least 8 A.D., - * and perhaps as late at the 4th century. Also, the beginning of a - * year varied from one culture to another - not all accepted January - * as the first month. - * - * CALENDAR OVERVIEW - * - * Julias Ceasar created the calendar in 46 B.C. as a modified form of - * the old Roman republican calendar which was based on lunar cycles. - * The new Julian calendar set fixed lengths for the months, abandoning - * the lunar cycle. It also specified that there would be exactly 12 - * months per year and 365.25 days per year with every 4th year being a - * leap year. - * - * Note that the current accepted value for the tropical year is - * 365.242199 days, not 365.25. This lead to an 11 day shift in the - * calendar with respect to the seasons by the 16th century when the - * Gregorian calendar was created to replace the Julian calendar. - * - * The difference between the Julian and today's Gregorian calendar is - * that the Gregorian does not make centennial years leap years unless - * they are a multiple of 400, which leads to a year of 365.2425 days. - * In other words, in the Gregorian calendar, 1700, 1800 and 1900 are - * not leap years, but 2000 is. All centennial years are leap years in - * the Julian calendar. - * - * The details are unknown, but the lengths of the months were adjusted - * until they finally stablized in 8 A.D. with their current lengths: - * - * January 31 - * February 28/29 - * March 31 - * April 30 - * May 31 - * June 30 - * Quintilis/July 31 - * Sextilis/August 31 - * September 30 - * October 31 - * November 30 - * December 31 - * - * In the early days of the calendar, the days of the month were not - * numbered as we do today. The numbers ran backwards (decreasing) and - * were counted from the Ides (15th of the month - which in the old - * Roman republican lunar calendar would have been the full moon) or - * from the Nonae (9th day before the Ides) or from the beginning of - * the next month. - * - * In the early years, the beginning of the year varied, sometimes - * based on the ascension of rulers. It was not always the first of - * January. - * - * Also, today's epoch, 1 A.D. or the birth of Jesus Christ, did not - * come into use until several centuries later when Christianity became - * a dominant religion. - * - * ALGORITHMS - * - * The calculations are based on two different cycles: a 4 year cycle - * of leap years and a 5 month cycle of month lengths. - * - * The 5 month cycle is used to account for the varying lengths of - * months. You will notice that the lengths alternate between 30 and - * 31 days, except for three anomalies: both July and August have 31 - * days, both December and January have 31, and February is less than - * 30. Starting with March, the lengths are in a cycle of 5 months - * (31, 30, 31, 30, 31): - * - * Mar 31 days \ - * Apr 30 days | - * May 31 days > First cycle - * Jun 30 days | - * Jul 31 days / - * - * Aug 31 days \ - * Sep 30 days | - * Oct 31 days > Second cycle - * Nov 30 days | - * Dec 31 days / - * - * Jan 31 days \ - * Feb 28/9 days | - * > Third cycle (incomplete) - * - * For this reason the calculations (internally) assume that the year - * starts with March 1. - * - * TESTING - * - * This algorithm has been tested from the year 4713 B.C. to 10000 A.D. - * The source code of the verification program is included in this - * package. - * - * REFERENCES - * - * Conversions Between Calendar Date and Julian Day Number by Robert J. - * Tantzen, Communications of the Association for Computing Machinery - * August 1963. (Also published in Collected Algorithms from CACM, - * algorithm number 199). [Note: the published algorithm is for the - * Gregorian calendar, but was adjusted to use the Julian calendar's - * simpler leap year rule.] - * - **************************************************************************/ - -#include "sdncal.h" - -#define SDN_OFFSET 32083 -#define DAYS_PER_5_MONTHS 153 -#define DAYS_PER_4_YEARS 1461 - -void SdnToJulian( - long int sdn, - int *pYear, - int *pMonth, - int *pDay) -{ - int year; - int month; - int day; - long int temp; - int dayOfYear; - - if (sdn <= 0) { - *pYear = 0; - *pMonth = 0; - *pDay = 0; - return; - } - temp = (sdn + SDN_OFFSET) * 4 - 1; - - /* Calculate the year and day of year (1 <= dayOfYear <= 366). */ - year = temp / DAYS_PER_4_YEARS; - dayOfYear = (temp % DAYS_PER_4_YEARS) / 4 + 1; - - /* Calculate the month and day of month. */ - temp = dayOfYear * 5 - 3; - month = temp / DAYS_PER_5_MONTHS; - day = (temp % DAYS_PER_5_MONTHS) / 5 + 1; - - /* Convert to the normal beginning of the year. */ - if (month < 10) { - month += 3; - } else { - year += 1; - month -= 9; - } - - /* Adjust to the B.C./A.D. type numbering. */ - year -= 4800; - if (year <= 0) - year--; - - *pYear = year; - *pMonth = month; - *pDay = day; -} - -long int JulianToSdn( - int inputYear, - int inputMonth, - int inputDay) -{ - int year; - int month; - - /* check for invalid dates */ - if (inputYear == 0 || inputYear < -4713 || - inputMonth <= 0 || inputMonth > 12 || - inputDay <= 0 || inputDay > 31) { - return (0); - } - /* check for dates before SDN 1 (Jan 2, 4713 B.C.) */ - if (inputYear == -4713) { - if (inputMonth == 1 && inputDay == 1) { - return (0); - } - } - /* Make year always a positive number. */ - if (inputYear < 0) { - year = inputYear + 4801; - } else { - year = inputYear + 4800; - } - - /* Adjust the start of the year. */ - if (inputMonth > 2) { - month = inputMonth - 3; - } else { - month = inputMonth + 9; - year--; - } - - return ((year * DAYS_PER_4_YEARS) / 4 - + (month * DAYS_PER_5_MONTHS + 2) / 5 - + inputDay - - SDN_OFFSET); -} |