[Libreoffice-bugs] [Bug 127334] Regression: Incompatible changes in date/time arithmetic introduced between Version: 6.0.4.2 (x64) and version 6.2.6.2 (ubuntu)

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=127334

Albrecht Müller <albrecht.mueller at astrail.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|CLOSED                      |REOPENED
         Resolution|FIXED                       |---
     Ever confirmed|0                           |1

--- Comment #5 from Albrecht Müller <albrecht.mueller at astrail.de> ---
Eike Rathke confirmed the behaviour that I consider a bug. We differ in the
assessment of the consequences, however. That's why I reopened the Bug.

(In the history I saw that at 2019-09-04 18:57:20 UTC I had changed the
resolution from NOTABUG to FIXED - I was not aware that I did this and this
change was not intended)

After consulting the "Bug Priority Triage Flowchart Suggestion(s)" flowchart
(https://wiki.documentfoundation.org/images/0/06/Prioritizing_Bugs_Flowchart.jpg) 
I think its priority should be set to "Critical" for the following reasons:

- Loss of data:  Opening existing spreadsheets with the new version of Calc
will not reproduce the previous results (which were correct) any more. So these
results are lost.

- Broken core functions: I think doing correct calculations is a core function
of a spreadsheet. There seems to be a de facto standard how spreadsheet
programs deal with date/time calculations. This standard seems to work quite
well in practice so usually you don't have to worry about its limitations.
Previous versions of Calc adhered to this standard. This has been changed such
that you now get results that are wrong in about 50% of the cases. (Think of a
calculator that gives 0 or 1 with equal probability if you subtract two numbers
that differ by one).

It seems to be intended behaviour so I assume that it will appear always and on
clean installs. It affects all people that do floating point calculations on
time values and try to extract date/time-specific information like year, month,
day, hour, minute or second. Trivial calculations such as adding a date and a
time value and subtracting this from another combination of date and time are
sufficient to demonstrate the problem.

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