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Re: hold question

  • To: mathgroup at smc.vnet.net
  • Subject: [mg132335] Re: hold question
  • From: "Hans Michel" <hmichel at cox.net>
  • Date: Tue, 11 Feb 2014 02:58:42 -0500 (EST)
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Francisco:

Please look into a book on Calendrical Calculations by Edward Reingold,
Nachum Dershowitz

Some versions of their book also contains Mathematica code.

The following link is an excerpt see section 1.2 "Fixed Day Numbers"

http://assets.cambridge.org/97805218/85409/excerpt/9780521885409_excerpt.pdf
(Google Books [
http://books.google.com/books?id=5r_kSKE4OdYC&printsec=frontcover&source=gbs
_ge_summary_r&cad=0#v=onepage&q&f=false ])

The book can be overkill for such just solving your issues; but you stated
that".. dates is  always a pain ... in any language.."

Most computational language systems  that I am aware of, when relating to
date time, use a similar method of fixing the date and time to a number.

A properly formatted date and/or time cell (or column) in Excel  is really a
serialized date time in the back ground. So if you are always going to be
importing date columns in Excel you may choose to import the serialized
datetime.

See
http://mathematica.stackexchange.com/questions/527/is-it-possible-to-import-
dates-and-times-directly-as-absolutetime-and-by-pass-da

Hans
-----Original Message-----
From: Francisco Gutierrez [mailto:fgutiers2002 at yahoo.com] 
Sent: Monday, February 10, 2014 2:01 AM
To: mathgroup at smc.vnet.net
Subject: [mg132335] hold question

Dear Group:

Manipulating and importing/exporting dates is always a pain in the neck, in
any of the languages I am aware of. 
Mathematica has functions to work around many of these issues, and I was
actually able to complete the task I was involved in, but even then there is
an issue I obviously do not understand. 

Say I have this date in an Excel sheet: 01/08/2007. I import in into
Mathematica.  I want to prevent it from becoming an arithmetical expression,
so I sorround it by Unevaluated, HoldAll, and other hold-like devices, but I
do not obtain the desired result. The date becomes a division. 
For example, the output of HoldComplete[2+2] is  HoldComplete[2+2] , but
instead the output of HoldComplete[ 01/08/2007] is HoldComplete[1/(8x
2007)].

What I am overlooking?
(Mathematica 9.0)




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