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Update QTimeZone documentation on the limitations of MS's data

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Describe the work-around of ignoring claims of DST prior to 1900.

Change-Id: Ia8a2e6530b285cc8012423ba174fea47732e9ecb
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Jaishree Vyas <jaishree.vyas@qt.io>
This commit is contained in:
Edward Welbourne 2022-02-17 16:28:57 +01:00
parent 9a0949a25b
commit bc91be6a5f
1 changed files with 5 additions and 2 deletions
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7
src/corelib/time/qtimezone.cpp
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@ -169,8 +169,11 @@ Q_GLOBAL_STATIC(QTimeZoneSingleton, global_tz);
Windows native time zone support is severely limited compared to the
standard IANA TZ Database. Windows time zones cover larger geographic
areas and are thus less accurate in their conversions. They also do not
support as much historic conversion data and so may only be accurate for
the current year.
support as much historical data and so may only be accurate for the
current year. In particular, when MS's zone data claims that DST was
observed prior to 1900 (this is historically known to be untrue), the
claim is ignored and the standard time (allegedly) in force in 1900 is
taken to have always been in effect.
QTimeZone uses a conversion table derived form the Unicode CLDR data to map
between IANA IDs and Windows IDs. Depending on your version of Windows