Re: [Tzdist] Comments on timezone-service-11 sections 1 thru 4

[Ken Murchison <[e-mail]>]

On 08/20/2014 07:00 PM, Paul Eggert wrote:
>
> E.  Section 3.4 talks about truncation as if it applied only to past 
> data, but it also applies to the future.  For example, the tz database 
> currently truncates the data for "Asia/Tehran" after 2037, because 
> Iran's actual rules are based on the Persian calendar and cannot be 
> expressed compactly in tz format (or in VTIMEZONE format, I presume). 
> Worse, some rules are based on astronomical calendars and therefore 
> cannot be predicted into the indefinite future.

Hi Paul,

Just as an FYI, the Asia/Tehran rules could be compactly represented in 
VTIMEZONE using the RSCALE 
<http://tools.ietf.org/html/draft-daboo-icalendar-rscale> extension as 
below (RSCALE should be adopted by the CalExt WG shortly).  That being 
said, I don't think any automated tz data -> iCal converter (e.g. vzic) 
could generate this from the tz data as currently constituted unless it 
could parse and act upon the meta-data in the comments.

BEGIN:DAYLIGHT
TZNAME:IRDT
TZOFFSETFROM:+0330
TZOFFSETTO:+0430
DTSTART:19920322T000000
RRULE:RSCALE=PERSIAN;FREQ=YEARLY;BYMONTH=1;BYMONTHDAY=2
END:DAYLIGHT

BEGIN:STANDARD
TZNAME:IRST
TZOFFSETFROM:+0430
TZOFFSETTO:+0330
DTSTART:19910922T000000
RRULE:RSCALE=PERSIAN;FREQ=YEARLY;BYMONTH=6;BYMONTHDAY=31
END:STANDARD

-- 
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University