Hello, I am relatively new to RoR, but vastly experienced with time
zones
and date/time issues on other multiple other platforms.
I answer quite a few questions on StackOverflow in this area, and often
questions about ActiveSupport::TimeZone come up. I’m hoping that
someone
from this forum can provide the background behind this implementation,
such
that I am better informed to address these questions.
My understanding is that the Ruby TZInfo gem is the base implementation
of
the IANA/Olson time zone database, but Rails ships with
ActiveSupport::TimeZone which is based on this, with some changes. It’s
the changes that I’m unsure about.
From the documentation here:
The TimeZonehttp://api.rubyonrails.org/classes/ActiveSupport/TimeZone.html
class
serves as a wrapper around TZInfo::Timezone instances.
This is the basis for my earlier statements. But, WHY was it created?
Why
not just use the TZInfo gem?
It allows us to do the following:
Limit the set of zones provided by TZInfo to a meaningful subset of
146 zones.
Ok - but who determined which of the 578 zones are “meaningful”? By
what
criteria? And by what review process do newly established zones get
determined if they make the cut or not? Is there a recommended strategy
for
dealing with zones that were omitted?
Also, why limit it to begin with? The size of the database shouldn’t be
an
issue - since this is all server-side code. I could see perhaps
providing
a method to retrieve those that are “meaningful” from the larger data
set,
but it doesn’t make sense to me that they are omitted.
Retrieve and display zones with a friendlier name (e.g., Eastern
Timehttp://api.rubyonrails.org/classes/Time.html
(US & Canada) instead of America/New_York).
Again, who decides what “friendlier” means? I sure hope the original
names
are not lost - since those are keys used for interoperability with other
systems that also implement the TZDB. Are they still available on the
TimeZone object? What about non-English speakers, are these names
localized for them? Some of the names are quite reminiscent of the
Display
Names of the proprietary Microsoft Windows time zones. Did that have an
influence on their creation?
I see that the MAPPING constant is available in the documentation. That
is
good. I haven’t fully digested it though - is it a one-to-one mapping?
Does it handle TZDB link alias, such as Asia/Calcutta => Asia/Kolkata
or
US/Eastern => America/New_York ?
Thank you in advance for any and all information that you can provide.
-Matt Johnson