[date_time] recommending upgrading the timezone database

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[date_time] recommending upgrading the timezone database

Boost - Dev mailing list
The timezone database in Boost.DateTime doesn't have enough information in
it to be accurate all the time.  For example if a region changes time zone
rules, when applying timezone only the current rule will be applied
regardless of the date involved.  If a region stops using daylight savings
time, but a date/time falls before that rule change, it should still use
daylight savings in printed output, correct?

The IANA timezone database is more complete, and we could switch
Boost.DateTime to use that instead.  It is also maintained more frequently
than the built-in one, which was last updated 7 years ago, and 4 years
before that.

Any thoughts on this?

https://github.com/boostorg/date_time/issues/67

- Jim

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Re: [date_time] recommending upgrading the timezone database

Boost - Dev mailing list
On 7/01/2018 05:49, James E. King, III wrote:

> The timezone database in Boost.DateTime doesn't have enough information in
> it to be accurate all the time.  For example if a region changes time zone
> rules, when applying timezone only the current rule will be applied
> regardless of the date involved.  If a region stops using daylight savings
> time, but a date/time falls before that rule change, it should still use
> daylight savings in printed output, correct?
>
> The IANA timezone database is more complete, and we could switch
> Boost.DateTime to use that instead.  It is also maintained more frequently
> than the built-in one, which was last updated 7 years ago, and 4 years
> before that.
>
> Any thoughts on this?
>
> https://github.com/boostorg/date_time/issues/67

I recently came across these:
   - http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0355r0.html
   - https://github.com/HowardHinnant/date

While they're based around C++11+ and chrono rather than DateTime, they
do include support for the IANA timezone database; either downloaded,
shipped-with, or using the OS's copy.

Perhaps you could coordinate with him to include similar functionality
in DateTime, or to bring his library into Boost as a suggested C++11
replacement for DateTime (or everyone could just wait for C++20...)?


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