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)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net*References*: <QY6Y1n03A1r5Uyi01Y6ahP>

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)