On 11/30/16 21:02, Marshall Clow wrote:
On Wed, Nov 30, 2016 at 9:15 AM, Andrey Semashev <[email protected]>
wrote:
https://github.com/boostorg/date_time/pull/29 -- switch +/- on parsing.
Definitely correct, will break code.
I think we should fix bugs even if it breaks code. We could try to make it
less painful though.
I'm really reluctant to make this change. I see it breaking lots of
people's code for a small benefit.
Short synopsis:
There are two ways to describe a timezone difference from GMT (only two?
You must be mad! - Ok, two in this instance).
* Going west is negative. This reflects the fact that the time "gets
earlier" as you go west. In this scheme, San Diego is GMT-8, or "8 hours
behind GMT". When it's 8 AM in San Diego, then it's 4 PM in London. This is
what the ISO specifies. In my experience, this is what I see when people
want to use time zones.
* Going west is positive. This reflects the "amount of time that needs to
be added to the local time to get to GMT. In this scheme, San Diego is
GMT+8. This is what Posix specifies.
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap08.html
Boost.DateTime has a call named posix_time_zone
to_posix_string?
but it implements ISO time
zone semantics.
I asked Jeff Garland about this a while back, and he was horrified at the
idea of breaking everyone's code for this. His response was "Change the
docs, don't break code"
Thing is, the function have POSIX in its name, so POSIX semantics is
implied. Maybe we should create a new function and deprecate
to_posix_string? The new function could take an argument to select the
desired behavior.
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