Vpim talk - Feb 2007 - How to set TZID in DTSTART?

Hello all,

I am currently evaluating the vpim libraries and like them very much.  
However there''s one thing I can''t get done: How can I set the
TZID
parameter for DTSTART/END dates so my encoded ICS file looks  
something like this:

   BEGIN:VEVENT
   ...
   DTSTART;TZID=Eastern Time:20071201T080000
   DTEND;TZID=Eastern Time:20071207T110000
   ...
   END:VEVENT

I managed to create the VTIMEZONE object, but that only sets up the  
time-zone itself for reference. To actually use it, I need the TZID  
thing. UTC does not help me much ''caus I still need to tell the  
calendar in which time-zone the event happens so it can calculate the  
local time.

I found that I can create fields manually like this:

   f = Vpim::DirectoryInfo::Field.create(''DTSTART'',  
"20071201T080000", "TZID"=>"Eastern Time")
   f.to_s
   => "DTSTART;TZID=Eastern Time:20071201T080000\n"

That''s exactly the format I need. Then again I did not find out how  
to properly add that to the event object (i.e. event.dtstart(time,  
{"key" => "value"}) does not work).

This led me to monkey-patch the code (see below). I''m not deep into  
it and don''t get quite the structure of the code yet. So even the  
patch works in my setting, it could screw things.

I am grateful for any hints and pointers for an official way of  
adding the TZID parameter to date/time fields.

Andreas


--- i''m a monkeeey ---

module Vpim::Icalendar::Set::Util
   alias :original_set_date_or_datetime :set_date_or_datetime

   def set_date_or_datetime(name, default, value, params = {})
     props = original_set_date_or_datetime(name, default, value)
     params.each { |k,v| props.field(name)[k] = v }
     props
   end
end

module Vpim::Icalendar::Set::Common
   def dtstart(start, params = {})
     set_date_or_datetime ''DTSTART'',
''DATE-TIME'', start, params
     self
   end
end

class Vpim::Icalendar::Vevent::Maker
   def dtend(dtend, params = {})
     set_date_or_datetime ''DTEND'',
''DATE-TIME'', dtend, params
   end
end

Quoting monodeck at googlemail.com, on Wed, Feb 07, 2007 at 05:40:16PM
+0100:
> However there''s one thing I can''t get done: How can I set
the TZID
> parameter for DTSTART/END dates so my encoded ICS file looks  
> something like this:
> 
>    BEGIN:VEVENT
>    ...
>    DTSTART;TZID=Eastern Time:20071201T080000
>    DTEND;TZID=Eastern Time:20071207T110000
>    ...
>    END:VEVENT
I''ve never used timezones, or set tzids, so there is no API for them.
But, I''m painfully aware that TZ support is not good in vPim. Since I
started working on it, several very nice timezone/date support packages
with compiled in tz info have appeared on ruby forge.

Your approach seems completely workable. Do you think a full params
hash is required? It appears only ;tzid can be set (other than ;value,
which should be set already, and the magic hole, x- params).

Doesn''t a TZID have to map to a VTIMEZONE present in a calendar, to be
correctly encoded? Perhaps instead of a string, a Vtimezone object could
be passed:

 module Vpim::Icalendar::Set::Common
    def dtstart(start, timezone = nil)
    end
 end

And if there was an

  Icalendar#tz(tzid = nil) # nil means the single one, raise if there
  isn''t one

You could do

  cal.add_event(start, cal.tz) do |e| # event in the default timezone
    ...
  end

  cal.add_event(start) do |e| # event in "floating" time
    ...
  end

Just throwing ideas out, you''re the user, and the implementor,
I''m
afraid.  Time spent on vPim has become a time sink I can''t afford,
sorry. If you like, I can arrange commit access.

Cheers,
Sam

Hey Sam,
> > However there''s one thing I can''t get done: How can
I set the TZID
> I''ve never used timezones, or set tzids, so there is no API for
them.
I see. I''ve finally switchted to templates for generating calendar
files. I found it''s the quickest approach for my needs at the moment
(I don''t need parsing, but a lot of extra dirty X Outlook fields and
tweaks). Time zones however are very essential in my case since people
importing the ICS files are not in the same time zone.
> But, I''m painfully aware that TZ support is not good in vPim.
Since I
> started working on it, several very nice timezone/date support packages
> with compiled in tz info have appeared on ruby forge.
I''m not sure if it sould go as far as having a "real" time
zone
support (involving other libs). In my case i''d only need to say like:
"Dates and times for vevent x to be interpreted as local time in
time-zone y". So I''d be happy just having the API for supporting
VTIMEZONE and TZID wherever I need it.
> Do you think a full params hash is required? It appears only ;tzid can be
set
> (other than ;value, which should be set already, and the magic hole, x-
params).
If it''s constrained that way, the API shoudl reflect it of course.
> Just throwing ideas out, you''re the user, and the implementor,
I''m
> afraid.  Time spent on vPim has become a time sink I can''t afford,
> sorry. If you like, I can arrange commit access.
Same here. I need a day that counts 48 hours, then I would have
OpenSource time again. But i''ll send you a patch along as soon as the
"tempalte" approach gets to awkward and I need somthing more
contained.

Thanks you took the time to answer.
Andreas