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Subject: Re: [office] ODD{F,L}, Yield and Price spreadsheet functions.
And if one wants to update a document to use another convention, how would the user change the table:null-date value? Is this something that would appear in the format dialogs? wt On Thu, May 15, 2008 at 6:45 AM, <robert_weir@us.ibm.com> wrote: > > > "Andreas J. Guelzow" <aguelzow@math.concordia.ab.ca> wrote on 05/15/2008 > 12:48:07 AM: > >> Is there any descriptions somewhere how this is supposed to work in the >> context of importing files from other common formats? >> >> Imagine: [.A1] 34556 >> [.A2] 56643 >> [.A3] =[.A1] - 3 * [.A2] >> [.A4] =DAYS360([.A1];[.A2]) > > The only interesting thing here is in A4, where there is an implicit > conversion from a number to a date. The other calculations are purely > numeric. > > Excel will do this conversion differently based on whether the spreadsheet > is in 1900-mode or 1904-mode. This was originally a Windows versus Mac > distinction. > > OOXML has a different set of modes: > > 1900 date base system -- expresses years from -9999 to 99999 with origin at > December 30th, 1899 = 0 > > 1900 backward compatibility system -- expresses years from 1900 to 9999 with > January 1st, 1900 = 1 (default system) > > 1904 backwards compatibility system -- expresses years from 1904 to 9999 > with January 1st, 1904 = 0. > > Only the default mode is implemented in Excel 2007. > > So realistically, all a convertor needs to worry about today is the > 1900/1904 distinction. > > An ODF table (including a spreadsheet) allows a table:null-date element that > specifies the date original, i.e., what date is equivalent to the number 0. > The default value is 1899-12-30. So this would be the same as the 1900 > date base system in OOXML. > > So in the case of importing an existing Excel document, the easiest thing > for a convertor to do would be to set the table:null-date value in the ODF > document to correspond to the conventions used by the source Excel document. > > The hard case would be when importing content from multiple source Excel > documents into a single ODF document, say one using 1900 conventions, one > using 1904 conventions, one using OOXML conventions, etc. I don't think > this works even if you did it all in Excel. > > Generally, relying on the details of implementation's numeric-to-date > conversions will result in a non-portable document. > > -Rob >
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