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Full Discussion: Doubt in datecalc.....
Top Forums UNIX for Dummies Questions & Answers Doubt in datecalc..... Post 302287557 by Perderabo on Saturday 14th of February 2009 07:04:21 AM
Old 02-14-2009
I wrote those functions and I cannot explain them. I surfed the web and found date calculation routines in a variety of languages. I converted to ksh and benchmarked them. I took the fastest routines and used them. I gave datecalc a finite range, 1860 to 3999. 1860 is when the US bought Alaska and mandated that Alaska migrate from the julian to the gregorian calendar. Whether or not the year 4000 will be a leap year is controversial.

I manually verified that Jan 1, 1860 works right. Then I used a verification script to generate the dates between 1860 and 3999 by incrementing the day, month, and year. Each date was fed to datecalc for conversion to modified julian day. The script verified that the mjd incremented by 1 each day. The mjd was fed to datecalc for conversion back to year, month, and day and this final output was compared to the original date. So I know for sure that the routines work between the limits I set.

I don't understand the algorithms. But I know that they work. Calendar algorithms are not worth studying. Why not study an interesting algorithm instead? For example: how to accurately calculate x^y in extended floating point using only extended floating point for all intermediate calculations? I've been trying to figure that one out all week. It's much harder than it looks.
 

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LEARN ABOUT DEBIAN

pltimefmt

PLTIMEFMT(3plplot)						    PLplot API							PLTIMEFMT(3plplot)

NAME

       pltimefmt - Set format for date / time labels

SYNOPSIS

       pltimefmt(fmt)

DESCRIPTION

       Sets the format for date / time labels. To enable date / time format labels see the options to plbox(3plplot) and plenv(3plplot).

       Redacted form: pltimefmt(fmt)

       This function is used in example 29.

ARGUMENTS

       fmt (const char *, fmt)
	      This string is passed directly to the system strftime. See the system documentation for a full list of conversion specifications for
	      your system. All conversion specifications take the form of a '%' character followed by further conversion specification	character.
	      All other text is printed as-is. Common options include: %c: The preferred date and time representation for the current locale.  %d:
	      The day of the month as a decimal number.  %H: The hour as a decimal number using a 24-hour clock.  %j: The day of  the  year  as  a
	      decimal  number.	 %m: The month as a decimal number.  %M: The minute as a decimal number.  %S: The second as a decimal number.  %y:
	      The year as a decimal number without a century.  %Y: The year  as a decimal number including a century.

AUTHORS

       Geoffrey Furnish and Maurice LeBrun wrote and maintain PLplot.  This man page was automatically generated from the DocBook  source  of  the
       PLplot documentation, maintained by Alan W. Irwin and Rafael Laboissiere.

SEE ALSO

       PLplot documentation at http://plplot.sourceforge.net/resources.

								   August, 2012 						PLTIMEFMT(3plplot)
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