iw3jdn.f File Reference

Computes julian day number from year (4 digits), month, and day. More...

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Functions/Subroutines
function	iw3jdn (iyear, month, iday)
	Computes julian day number from year (4 digits), month, and day.

Detailed Description

Computes julian day number from year (4 digits), month, and day.

Author

Ralph Jones

Date

1987-03-29

Definition in file iw3jdn.f.

Function/Subroutine Documentation

iw3jdn()

function iw3jdn	(		iyear,
			month,
			iday
	)

Computes julian day number from year (4 digits), month, and day.

iw3jdn is valid for years 1583 a.d. to 3300 a.d. Julian day number can be used to compute day of week, day of year, record numbers in an archive, replace day of century, find the number of days between two dates.

Program history log:

• Ralph Jones 1987-03-29
• Ralph Jones 1989-10-25 Convert to cray cft77 fortran.

Parameters

[in]	IYEAR	Integer year (4 Digits)
[in]	MONTH	Integer month of year (1 - 12)
[in]	IDAY	Integer day of month (1 - 31)

Returns

IW3JDN Integer Julian day number

• Jan 1, 1960 is Julian day number 2436935
• Jan 1, 1987 is Julian day number 2446797

Note

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.

Author

Ralph Jones

Date

1987-03-29

Definition at line 41 of file iw3jdn.f.