The IW3JDN function computes julian day number.
USAGE: II = IW3JDN(IYEAR,MONTH,IDAY)
IYEAR ARG LIST INTEGER YEAR ( 4 DIGITS)
MONTH ARG LIST INTEGER MONTH OF YEAR (1 - 12)
IDAY ARG LIST INTEGER DAY OF MONTH (1 - 31)
IW3JDN FUNTION INTEGER JULIAN DAY NUMBER
JAN. 1,1960 IS JULIAN DAY NUMBER 2436935
JAN. 1,1987 IS JULIAN DAY NUMBER 2446797
Julian period was devised by Joseph Scaliger in 1582.
Julian day number #1 started on Jan. 1,4713 B.C. Three major
chronological cycles begin on the same day. A 28-year solar
cycle, a 19-year luner cycle, a 15-year indiction cycle, used
in ancient Rome to regulate taxes. It will take 7980 years
to complete the period, the product of 28, 19, and 15.
Scaliger named the period, date, and number after his father
Julius (not after the Julian calendar). This seems to have
caused a lot of confusion in text books. Scaliger name is
spelled three different ways. Julian date and Julian day
number are interchanged. A Julian date is used by astronomers
to compute accurate time, It has a fraction. When truncated to
an integer it is called an Julian day number. This function
was in a letter to the editor of the communications of the acm
volume 11 / number 10 / october 1968. The Julian day number
can be converted to a year, month, day, day of week, day of
year by calling subroutine W3FS26.
||Library contains Fortran 90 decoder/encoder
routines for GRIB edition 1. (Fortran90)
Date posted: 2/22/2007