5 replies to this topic

[andykay]

TRAHMA,

1/1/1800 is not equivilant to a Julian date of 000001.

Calendar Date 1/1/1800 = 2378497 Julian Date.

Julian Date 1 = 25/11/-4713 Calendar Date


I'm not sure how ProIV would do it (or why ), but here is how Java scripts do the calculation:

function compute(form) {
var y = parseFloat(form.year.value)
var m = parseFloat(form.month.value)
var d = parseFloat(form.day.value)
var uh = parseFloat(form.uth.value)
var um = parseFloat(form.utm.value)
var us = parseFloat(form.uts.value)

var extra = 100.0*y + m - 190002.5
var rjd = 367.0*y
rjd -= Math.floor(7.0*(y+Math.floor((m+9.0)/12.0))/4.0)
rjd += Math.floor(275.0*m/9.0)
rjd += d
rjd += (uh + (um + us/60.0)/60.)/24.0
rjd += 1721013.5
rjd -= 0.5*extra/Math.abs(extra)
rjd += 0.5
form.result.value = rjd



HTH,

AK

Edited by andykay, 07 June 2006 - 04:20 PM.

[Brian Manners]

G'day TRAHMA,

When you do a CDATE on the PRO-IV internal date of 1, you will get the 1st Jan 1800. Each day then increments PRO-IV's internal counter by 1. So today it's been 75399 days since the counter started.

I would assume PRO-IV created this structure to allow easy date ordering within PRO-ISAM files when specifying dates as keys to tables etc.

The version of PRO-IV we're using (Version : 5.0000 1.0.9) has a maximum of 438291 or 31/12/2999

So watch out for that 3K bug !!

Edited by Brian Manners, 07 June 2006 - 10:53 PM.

[Yann Blondaux]

When you do a CDATE on the PRO-IV internal date of 1, you will get the 1st Jan 1800. Each day then increments PRO-IV's internal counter by 1. So today it's been 75399 days since the counter started.

ProIV is really an old language
Now the counters are incremented automatically but in the beginning of the 18' there were a whole range of old women sitting in a drugstore pushing on a huge handle to increment the CDATE counter.

(Sorry, I couldn't help it)

Edited by Yann Blondaux, 08 June 2006 - 06:39 AM.

[Chris Pepper]

There's lots of base dates out there!

Unix has 1 June 1970,

Excel has 1 January 1990 (on the pc) and for some bizarre reason it has 1 January 1904 on the Mac!

(that reminds me of the time when ProIV had different base dates on the mainframe & other systems!).

[Richard Bassett]

See the "Trivia" section at the end of the Wikipedia entry for "Epoch"

OP, note ProIV does not support -ve date values <_<

BTW, if it's "genuine" Julian dates you're interested in and you're using Oracle then ISTR there is some useful "J" date format.

Edited by Richard Bassett, 08 June 2006 - 04:37 PM.