Parallel Gregorian/Julian JD Number Table Calculator Calendar Span: BC 19999-Jan-01-Tue/Thu  to  AD 19999-Dec-31-Fri/Sat PHP Program By Jay Tanner of Geneva, NY, USA

Gregorian Start Date

Days to Tabulate From Start   d

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Double-Click Within Text Area to Select ALL Text PARALLEL GREGORIAN/JULIAN JD NUMBER TABLE GREGORIAN_CALENDAR JD_Num | JULIAN_CALENDAR JD_Num | Diff ----------------------------- | ----------------------------- | ------ AD 02026-May-03-Sun 2461164 | AD 02026-May-03-Sat 2461177 | -13 d AD 02026-May-04-Mon 2461165 | AD 02026-May-04-Sun 2461178 | -13 d AD 02026-May-05-Tue 2461166 | AD 02026-May-05-Mon 2461179 | -13 d AD 02026-May-06-Wed 2461167 | AD 02026-May-06-Tue 2461180 | -13 d AD 02026-May-07-Thu 2461168 | AD 02026-May-07-Wed 2461181 | -13 d AD 02026-May-08-Fri 2461169 | AD 02026-May-08-Thu 2461182 | -13 d AD 02026-May-09-Sat 2461170 | AD 02026-May-09-Fri 2461183 | -13 d AD 02026-May-10-Sun 2461171 | AD 02026-May-10-Sat 2461184 | -13 d AD 02026-May-11-Mon 2461172 | AD 02026-May-11-Sun 2461185 | -13 d AD 02026-May-12-Tue 2461173 | AD 02026-May-12-Mon 2461186 | -13 d AD 02026-May-13-Wed 2461174 | AD 02026-May-13-Tue 2461187 | -13 d AD 02026-May-14-Thu 2461175 | AD 02026-May-14-Wed 2461188 | -13 d AD 02026-May-15-Fri 2461176 | AD 02026-May-15-Thu 2461189 | -13 d AD 02026-May-16-Sat 2461177 | AD 02026-May-16-Fri 2461190 | -13 d AD 02026-May-17-Sun 2461178 | AD 02026-May-17-Sat 2461191 | -13 d ----------------------------- | ----------------------------- | ------ GREGORIAN_CALENDAR JD_Num | JULIAN_CALENDAR JD_Num | Diff

Double-Click Within Text Area to Select ALL Text This program displays a parallel table of signed Gregorian and Julian JD Numbers for both the modern Gregorian calendar and the old Julian Calendar. ############################################################################## The 'Diff' column is the number of days (Gregorian − Julian) to apply to the Julian calendar JD number to obtain the corresponding JD Number on the Gregorian calendar. The difference between the calendars is due to the differences in their rules used to handle leap years and the fact that 10 days were dropped from the cal- endar during the Julian to Gregorian calendar transition in October of 1582 to realign the calendar date of spring (March 21) with the sun again. According to the calendar, spring had drifted to occuring 10 days too early due to the old Julian calendar leap year rule being slightly off by 1 day every 400 years and not being corrected for over 1600 years, until mid-October of 1582. ------------------------------ JULIAN CALENDAR LEAP YEAR RULE Every year that is divisible by 4 is a leap year without exception, including all century years (years ending in -00). --------------------------------- GREGORIAN CALENDAR LEAP YEAR RULE Every year BETWEEN century years that is divisible by 4 is a leap year, but every century year (ending in -00) is a leap year ONLY if it is divisible by 400, otherwise it is a common year. On our modern Gregorian calendar, only one century year out of every 400 years is a leap year. The century year AD 1600 was a leap year. The century year AD 2000 was a leap year. That will not happen again until the year AD 2400. ############################################################################## THE DAYS OF THE WEEK To find the weekday (Sun to Sat), from the signed JD Number value, we compute its cyclic weekday index number starting from Sunday (DoWi = 0). Let: JDNum = Signed Julian Day Number (Span: -5583059 to 9025909) DoWi = DayOfWeek index (0 to 6) Where: 0=Sun, 1=Mon, 2=Tue, 3=Wed, 4=Thu, 5=Fri and 6=Sat DoWi = (7 + ((JDNum + 1) mod 7)) mod 7 Given a source string of 3-letter weekday abbreviations, like: WEEKDAYS = 'SunMonTueWedThuFriSat' The DoWi index value gives us a pointer to where the 3-letter abbreviation is located within the WEEKDAYS string. For example, if the DoWi value is 5, then it refers to 'Fri' at string index location 3*DoWi = 3*5 = 15. This says that the 3-letter abbreviation for Friday ('Fri') starts at string character index 15 within the WEEKDAYS source string. Text strings are indexed from zero in most computer languages, by default. The 3 refers to the number of characters in each weekday abbreviation substring.

PHP Program by PHP Program By Jay Tanner of Geneva, NY, USA v1.00 - Revised: 1970-January-01-Thursday at Local Time 12:00:00 AM (UTC−05:00)