[tz] Support for the IANA database in the Python standard library

Ken Murchison murch at fastmail.com
Wed Feb 26 23:09:30 UTC 2020

On 2/26/20 5:40 PM, Brian Inglis wrote:
> On 2020-02-26 14:31, Paul Eggert wrote:
>> On 2/25/20 6:40 PM, Paul Ganssle wrote:
>>> My main concern is that my hope is to try to use a time zone data source that
>>> can be managed at the system level, independent of language stack. I will
>>> admit to never having looked into the details, but I was under the impression
>>> that tzdist was something that the system would consume, rather than
>>> individual programs, is that wrong?
>> As a protocol, tzdist can be used both by individual programs and by the system.
>> It's still pretty new and I don't know of any census, but at least Cyrus
>> supports it so that clients can have the latest tzdata even if their OS tzdata
>> is out-of date; see
>> <https://www.cyrusimap.org/imap/download/installation/http/caldav.html>.
> Reading that, Cyrus supports converting tz data sources to iCalendar data with
> vzic which it then makes available via CalDAV for calendar clients; it does not
> appear to support zoneinfo binary data or TzDist for tzdata clients:
> "This module is designed to use the IANA Time Zone Database data (a.k.a. Olson
> Database) converted to the iCalendar format.
> Cyrus uses a modified vzic to convert IANA formatted data into iCalendar format."
> and predates TzDist:
> "recently downloaded time zone data (e.g. “IANA Time Zone Database v.2013h”)"
> The CMU server no longer appears to be available.

The Cyrus server is no longer actively developed at CMU, but it is still 
being actively developed, mostly by Fastmail and is available at GitHub 
(the FTP repository at CMU has been shut down).

The TZdist module (written by me while at CMU) WILL return TZif data if 
requested, but I haven't updated the documentation to match the latest 
code - we don't use it yet at Fastmail so this task hasn't reached the 
top of my list.

I've also been meaning to write a client to update zoneinfo by fetching 
TZif data from a TZdist server, but have yet to do so.


Ken Murchison
Cyrus Development Team
Fastmail US LLC

More information about the tz mailing list