[Libreoffice-bugs] [Bug 144699] New: Use proleptic Gregorian consistently for *all* date formatting and recognition

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=144699

            Bug ID: 144699
           Summary: Use proleptic Gregorian consistently for *all* date
                    formatting and recognition
           Product: LibreOffice
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: medium
         Component: LibreOffice
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: mikekaganski at hotmail.com
                CC: andreas.heinisch at yahoo.de, erack at redhat.com

Bugs 96756, 144678, 144687, 144692 show some of the problems arising from our
use of ICU's default Julian cutover date, which is 1582-10-15. There are more
to it, e.g. there's no way to be ISO-8601-compatible using YYYY-MM-DD format,
because ISO 8601 requires that all dates are sequential, while we have a
sequence break around the cutover.

Note that the described problems are not limited to Calc; all modules use the
same formatter to recognize and display dates.

It seems that it would be useful to not try to solve those bugs by making them
honor Julian calendar (that would need additional complexity, and would not
solve every problem); LibreOffice is not a tool that is intended to demonstrate
*some* specific historical event when displaying dates (at least by default).

The proposal is to use proleptic Gregorian calendar for all the representable
date range in LibreOffice; that would make all the mentioned problems to get
resolved automatically, introducing consistency.

To not break existing documents, we likely need a new option (common to all ODF
document types), like "Use proleptic Gregorian for all dates". It should be
enabled by default in new documents, as well as in all imported documents
(e.g., Excel does not format dates prior to 1900-01-01, so there may no
compatibility issues with XLS(X) documents); but existing ODF documents, where
there's no such flag defined, should be treated as before.

The option should *possibly* be located near current "Year (Two Digit)"
configuration option on General page (however, the latter option is not
document-specific, so my idea could be wrong; anyway, the location should be
common/independent for all modules).

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