There are GMT-offset zones whose convention for the sign of the offset
is the reverse of what we are (still) using, which is the usual
convention for UTC-offset zone: for example, the Olson Database's
Etc/GMT+3 has offset -3 hours in the UTC-based system we use, so we
give it suffix GMT-0300. The UTC-based suffix is also what we use as
the abbreviation for OffsetFromUTC() in toString().
For now this only adds support for parsing a planned future form: the
old form using GMT is retained, to give client code some chance to
prepare for a backwards-compatible transition. Although the GMT prefix
is matched case-insensitively, only match UTC if fully upper-case;
there is no meaningful precedent for case-insensitive usage here.
[ChangeLog][QtCore][QDateTime] The Qt::TextDate format now recognizes
UTC-based offset suffixes in addition to suffixes based on the
deprecated alias GMT. This prepares for toString() to use such
UTC-based suffixes for time-zones (fromString() cannot parse the
present abbreviation suffix). A future release of Qt shall use
UTC-based suffixes in place of the present GMT-based suffixes (which
conflict with GMT-based IANA zone names) for Qt::LocalTime and
Qt::OffsetFromUTC time-specs. Client code is encouraged to use and
recognize UTC-based zone suffixes in preparation for that transition,
unless compatibility with versions before 6.2 is required.
Change-Id: I5a42a488f1232a30f4b427b7954759283423b9b3
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
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