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WP34S JG1582 / JG1752
Message #1 Posted by M. Joury on 13 Oct 2011, 11:37 p.m.

I am trying to figure out what exactly these modes do. Per the manual they are supposed to effect the calculation of J-D and D-J but they don't appear to make any difference on my machine. What am I missing? I'm currently running build 1630.

Cheers,

-Marwan

      
Re: WP34S JG1582 / JG1752
Message #2 Posted by Paul Dale on 13 Oct 2011, 11:42 p.m.,
in response to message #1 by M. Joury

These two set the assumed change over date between the Julian and Gregorian calendars for purposes of the other date commands.

- Pauli

            
Re: WP34S JG1582 / JG1752
Message #3 Posted by M. Joury on 14 Oct 2011, 7:00 a.m.,
in response to message #2 by Paul Dale

Right, but shouldn't they effect what J-D and D-J return? J-D and D-J seem to return the same value for either setting in my case. How can I verify that the change in setting took place? Can't seem to find that in the manual.

Example: With Either JG mode setting and for the date 10.142011 (today US date format) they both return 2,455,849.

Thanks,

-Marwan

                  
Re: WP34S JG1582 / JG1752
Message #4 Posted by Marcus von Cube, Germany on 14 Oct 2011, 7:05 a.m.,
in response to message #3 by M. Joury

Try a date before the switch-over date. The Julian day should be different only between 1582 and 1752.

                        
Re: WP34S JG1582 / JG1752
Message #5 Posted by M. Joury on 14 Oct 2011, 7:14 a.m.,
in response to message #4 by Marcus von Cube, Germany

Ah. Like I said in my original post: "What am I missing." Makes sense now that you put it into words. Silly misunderstanding.

Thanks,

-Marwan

                        
Re: WP34S JG1582 / JG1752
Message #6 Posted by Bart (UK) on 14 Oct 2011, 7:30 a.m.,
in response to message #4 by Marcus von Cube, Germany

Quote:
The Julian day should be different only between 1582 and 1752
Yes, and choosing JG1582 or JG1752 depends on when the Gregorian calendar was adopted in which country. Some adopted in 1582 and others only in 1752. So knowing which implementation to use depends on both the year you wish to convert and knowledge of where that date originated.
                  
Re: WP34S JG1582 / JG1752
Message #7 Posted by Bart (UK) on 14 Oct 2011, 7:17 a.m.,
in response to message #3 by M. Joury

And so it should.

The implementations depend on finding the JD for years before 1582 and 1752, when the Gregorian Calendar was adopted, depending on country.

Perhaps the "notes" in the following reference will shed some light on the subject.Julian Date Converter

                  
Re: WP34S JG1582 / JG1752
Message #8 Posted by Dieter on 14 Oct 2011, 7:25 a.m.,
in response to message #3 by M. Joury

Sure - you will get the same result for any date after 1752. ;-)

In 1582 pope Gregory XIII introduced the calendar we still use today - the Gregorian calendar. The official switch date was Friday, 15 October 1582 which followed directly on Thursday, 4 October. The dates inbetween are not defined.

While the new calendar was adopted in many countries (e.g. most of Europe) in 1582 or shortly after, the British Empire did not do so before September 1752. So the years between 1582 and 1752 will cause different results because the countries that had switched early already had the Gregorian calendar while in the British Empire still the old Julian calendar was valid.

Before this flag was introduced the 34s generally assumed a switch in 1752, i.e. the date valid only for the British Empire. Today at least the official (and IMHO only correct) date can be set. Users in countries that did not adopt the Gregorian calendar on these two dates will only get correct results for dates after the one their country switched.

Dieter

                        
Re: WP34S JG1582 / JG1752
Message #9 Posted by M. Joury on 14 Oct 2011, 9:12 a.m.,
in response to message #8 by Dieter

Thanks you for all the responses and explanations. I had never worked with Julian dates between 1582 and 1752 and so missed the point.

Cheers,

-Marwan

                        
Re: WP34S JG1582 / JG1752
Message #10 Posted by Walter B on 14 Oct 2011, 5:28 p.m.,
in response to message #8 by Dieter

Quote:
While the new calendar was adopted in many countries (e.g. most of Europe) in 1582 or shortly after, the British Empire did not do so before September 1752.
So it took them 170 years extra. Applying this to metric units, the US of A are a bit overdue, aren't they? (Sorry, couldn't resist ;-)
                              
Re: WP34S JG1582 / JG1752
Message #11 Posted by M. Joury on 14 Oct 2011, 6:48 p.m.,
in response to message #10 by Walter B

The non-metric nature of US units drives me insane! Metric is just so much more logical. The best (sarcasm on) is having to have two sets of tools to work on European cars (which is all we own) and bicycles (that are all metric) plus all the other things around the house that are not. I wonder how much this would reduce costs for US corporations if they would just get it over with and switch over.

Cheers,

-Marwan

                  
Re: WP34S JG1582 / JG1752
Message #12 Posted by Paul Dale on 14 Oct 2011, 9:43 a.m.,
in response to message #3 by M. Joury

These settings also impact the other date functions not just the J-D and D-J ones.

- Pauli


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