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WP34s: date functions and negative years
01-17-2015, 09:47 PM (This post was last modified: 01-17-2015 10:04 PM by Dieter.)
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RE: WP34s: date functions and negative years
(01-17-2015 09:25 PM)walter b Wrote:  Oh dear, that 34S project confronts me with problems I didn't even know before Wink

That's what this forum is all about.

Quote:Seriously, JD 0 was defined to cover all recorded human astronomical observations IIRC. OTOH, how shall the poor WP 34S know that an input of -1.012345 (in D.MY or M.DY) shall mean New Year's day of the year 2345 B.C.?

Well, it does know this when it returns exactly this result after 864547 D–>J. Even though it returns the wrong day of week. Since days and months are always positive, the sign must belong to the year. That's how the 34s already handles negative dates under certain circumstances.

The 34s, as it is, already returns negative years, so why cannot the user enter the same? Why does the 34s not accept its own (negative) output as valid input for further calculations? And why is the 34s partially wrong? Try 1 Jan 1 BC (a Thursday) and subtract exactly 52 weeks = 364 days: 1.010000 ENTER –364 DAYS+ returns –2.010001 (correct) and "Sunday" (wrong, should be Thursday again).

BTW your example –1.012345 does not refer to 2345 B.C., but 2346 B.C. (the year before 1 AD is 1 BC = year 0).

Quote:There's a reason why ISO defined Y.MD as standard format for dates.

The problems I mentioned occur regardless which date format is set.
And BTW, ISO also defines a proleptic Gregorian (!) calendar. Would you prefer such a solution?


I think the 34s is a serious project and so we should talk about problems seriously. Some of the problems and inconsistencies are listed in my first post. Yes, the device - as it is now - returns results that are simply wrong. Not more, not less. That's why it should be fixed. The one way or the other. Either negative years are rejected with an error message or they have to be handled correctly. Tertium non datur. Do you disagree?

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RE: WP34s: date functions and negative years - Dieter - 01-17-2015 09:47 PM

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