[see also: recurrence.txt GUPE/iCalendar.pm]

=head1 Overviews

  http://en.wikipedia.org/wiki/ICalendar
  http://developer.apple.com/internet/appleapplications/icalendarfiles.html
  http://muddybranch.thejkgroup.com/ http://www.intellical.com/ Jason Klemow
  http://www.calconnect.org/resultsfromrecurrencequestionnaire.pdf

=head1 Standards Bodies and Consortia

  http://www.calconnect.org/

=head1 Standard Formats

  Google Base has a set of attributes at: http://base.google.com/base/atom_specs.html
     also CSV and RSS, see http://base.google.com/base/howtobulkupload.html
  Google Calendar http://www.google.com/calendar  
    http://groups.google.com/group/google-calendar-help-dataapi
    http://code.google.com/apis/gdata/overview.html
    has XML export.
    uses Atom, with extra namespaces:
       xmlns:gd='http://schemas.google.com/g/2005'
       xmlns:gCal='http://schemas.google.com/gCal/2005'
     gd:when
     gd:recurrence
     gCal:timezone
  vCalendar (1.0 September 18, 1996) http://www.imc.org/pdi/vcal-10.txt
  iCalender http://www.ietf.org/rfc/rfc2445.txt
  xCal aka xCalendar         http://xml.coverpages.org/iCal.html
    Frank Dawson 2002
       http://www.globecom.net/ietf/draft/draft-dawson-ical-xml-dtd-01.html
    Dawson, Reddy, Royer, Plamondon 2002 "iCalendar DTD Document (xCal)"
       http://www.ietf.org/internet-drafts/draft-ietf-calsch-many-xcal-02.txt
       http://www.calsch.org/ietf/archives/draft-ietf-calsch-many-xcal-02.html
       implemented in Mozilla Calendar, but not much pickup.
       DTD for mapping of iCalendar
    T. Hare 2005 "Guideline for use of XML with iCalendar elements"
       http://ietfreport.isoc.org/idref/draft-hare-xcalendar/
       http://www.ietf.org/internet-drafts/draft-hare-xcalendar-03.txt
       uses attributes for vcalendar prodid and version
       defines a "-//IETF//DTD XCAL/iCalendar XML//EN" iCalendar dtd
       uses attributes for parameters
    D. Royer 2005 "iCalendar in XML Format (xCal-Basic)"
       http://inet-consulting.com/xcal.html 
       draft-royer-calsch-xcal-02
       puts prodid and version in elements
       uses lowercase for tag names but upper case for param values like role="CHAIR" and rrule content like BYDAY
    XML schema here:  http://sw.sbay.org/xml/    http://sw.sbay.org/xml/xcal-20040224.xsd
  SKICal http://skical.metamatrix.se/
    swedish; some good enhancements related to public events
  "RDF Calendar"
    http://esw.w3.org/topic/RdfCalendar 
    http://www.w3.org/2002/12/cal/
    http://www.w3.org/TR/rdfcal/
  hCalendar http://developers.technorati.com/wiki/hCalendar
     http://microformats.org/wiki/hcalendar-brainstorming
     xhtml encoding
  iCalendar Basic http://www.ietf.org/internet-drafts/draft-royer-ical-basic-03.txt
     simplifies iCalendar
  http://xml.coverpages.org/draft-royer-ical-vcard-01.txt
        Using VCARDs with iCalendar
        allows ATTENDEE;VCARDURL="https:cal.example.com/user?uid=vcard=123.vcf":CAP:Doug@Royer.com
  http://www.iptc.org/EventsML/
     seems to have died

  Regarding vCard and XML:
    http://xml.coverpages.org/vcard.html
	overview
    draft-dawson-vcard-xml-dtd-0[0-3]
	http://www.watersprings.org/pub/id/draft-dawson-vcard-xml-dtd-03.txt
	<vCard xmlns:xcfxml='http://www.ietf.org/internet-drafts/draft-dawson-vcard-xml-dtd-04.txt'>
	   <n><family>Dawson</family> <given>Frank</given></n>
	   <org><orgname>Lotus Development Corporation</orgname>
	   <adr adr.type="WORK POSTAL PARCEL">
	     <street>6544 Battleford Drive</street>
             <locality>Raleigh</locality>
             <region>NC</region>
             <pcode>27613-3502</pcode>
             <country>USA</country>
           </adr>
	   <tel tel.type="WORK MSG PREF">+1-617-693-8728</tel>
    http://www.jabber.org/jeps/jep-0054.html
	carrying forward from Dawson
	elements names are upper case
	version is an attribute
	params are self-closing element children
	namespace is vcard-temp

=head1 Standard Protocols

CalDAV http://greenbytes.de/tech/webdav/draft-dusseault-caldav-01.html

http://www.faqs.org/rfcs/rfc2446.html
        iCalendar Transport-indendent Interoperability Protocol (iTIP)
        static and dynamic event, to-do, journal and free/busy objects
        either store and forward (imip) or real-time
        CU calendar user to CU communication
        CUA and CS

http://www.faqs.org/rfcs/rfc2447.html
        [iMIP] specifies an Internet email binding for [iTIP].

http://www.ietf.org/internet-drafts/draft-ietf-calsch-cap-02.txt
        CAP Calendar Access Protocol
        the CUA to CS communication
IRIP
        real-time analog of imip. maybe being superseded by CAP?

ICAP - defunct proposal (96), see http://www.clearblue.com/draft-oleary-icap-00.htm
     http://maelstrom.org.uk/
        Steve Ferris implemented ICAP java client and server, with source

other proposals:
      Scheduling Wide-area Transport Protocol SWTP http://www.p2software.com/
                 intranet consulting
      Simple Scheduling Transport Protocol (SSTP) presented by On Technology
             dead?

Calendaring and Scheduling Interoperability Protocol (CSIP) presented by OnTime/FTP Software
            now opentext
            web based

Internet Calendar Access Protocol (ICAP) presented by Clear Blue Network Systems and Lotus
         now criticalpath


=head1 Open Source Projects

 Name              Born  Died  URL 
 Free Association        2000  http://www.advogato.org/proj/Free%20Association/
 Reefknot                2001  http://reefknot.sourceforge.net/
 Hula              2005        http://www.hula-project.org/        Novell's old NetMail server
 OSA/Chandler      2003        http://www.osafoundation.org/

=head1 Articles and Link Farms

http://www.innerjoin.org/iCalendar/index.html

http://linuxmafia.com/faq/Apps/scheduling.html

DateLens http://www.cs.umd.edu/hcil/datelens/screenshots.shtml
         new design for a calendar
         requires .NET
	 got eaten by Microsoft: http://research.microsoft.com/news/monthlyfeature/datelens.aspx

http://www.w3.org/2001/sw/Europe/200210/calendar/vocab_usecases.html
        Semantic Web Calendaring vocabularies and usecases
        some interesting comments about the specs
        discusses iCalendar, xCalendar, SkiCap

http://www.idealliance.org/papers/xml2001/papers/html/05-04-06.html
	Calendaring and Scheduling with XML-RDF

draft-ietf-calsch-imp-guide-00.txt

Once more into the Breach: Calendars, Events and RSS 2003
    http://laughingmeme.org/archives/001224.html

rant about calendar support in evolution:
     http://luke.hates-software.com/2004/05/03/d940c010.html
     also digs at mozilla calendar

Scheduling Ourselves to Death
  http://www.kcoyle.net/schedule.html

=head1 Desired Features

Some desired features:

  categories
  email reminders
  indicate public and private when publishing
  publishing of free busy
  scheduling system (somehow)
  RSS feed
  handle recurring events
  handle multi-day and all-day events
  booking of rooms or other equipment
  send email to server to pick up an event (or pull from your email)
  pull in public holiday db (country-specific), and/or commemorative day db
  search by string in summary, qbe, etc. 
  merging of desired set of calendars
  control of sorting by: recur vs. recur, has start time and duration, has start time only, neither start time nor duration

=head1 Google Base

See 
    http://base.google.com/base/atom_specs.html
    http://base.google.com/base/attribute_list.html#event_date_range

  <g:event_date_range>
    <g:start>2005-12-20T14:00:00</g:start>
    <g:end>2005-12-20T19:00:00</g:end>
  </g:event_date_range>
 
  <g:expiration_date>2005-12-20</g:expiration_date>
  <g:expiration_date_time>2005-12-05T11:59:59</g:expiration_date_time>

  <g:location>1600 Amphitheatre Parkway, Mountain View, CA, 94043, USA</g:location>
  <g:location>37.423130,-122.083706</g:location>
   
  <g:image_link>http://example.com/images/1006.jpg</g:image_link>

See some discussion here:

  http://weblog.infoworld.com/udell/2006/06/13.html
  http://www.snellspace.com/wp/?p=314
    doesn't like the new elements vs just including xcal or hcalendar 
   
=head1 JiCal

See http://jical.sourceforge.net/

Has its own XML format that includes expanded events.

=head1 iCalendar RFC2445

See http://www.softwarestudio.org/iCal/2445Issues.html

Synctactically, iCalendar/vCalendar/vCard are similar.
It is roughly "field: value", though the field names can be parametrized. 
Field values can contain 8-bit characters. 
Lines can be LWS wrapped (lines SHOULD be no longer than 75 octets).

RFC 2445 grammar, in part:

    contentline        = name *(";" param ) ":" value CRLF
    name               = x-name / iana-token
    iana-token         = 1*(ALPHA / DIGIT / "-")
    x-name             = "X-" [vendorid "-"] 1*(ALPHA / DIGIT / "-")
    vendorid           = 3*(ALPHA / DIGIT)
    param              = param-name "=" param-value *("," param-value)
    param-name         = iana-token / x-token
    param-value        = paramtext / quoted-string
    paramtext          = *SAFE-CHAR
    value              = *VALUE-CHAR
    quoted-string      = DQUOTE *QSAFE-CHAR DQUOTE
    NON-US-ASCII       = %x80-F8
    QSAFE-CHAR         = WSP / %x21 / %x23-7E / NON-US-ASCII
    SAFE-CHAR          = WSP / %x21 / %x23-2B / %x2D-39 / %x3C-7E / NON-US-ASCII
    VALUE-CHAR         = WSP / %x21-7E / NON-US-ASCII

Values can contain escapes: \, \" \n

cal-address type examples (for example for ORGANIZER property):

     "MAILTO:jane_doe@host1.com"
     "CN=JohnSmith;DIR="ldap://host.com:6666/o=3DDC%20Associates,c=3DUS??(cn=3DJohn%20Smith)":MAILTO:jsmith@host1.com
     "ROLE=CHAIR:MAILTO:mrbig@host.com"

URL property examples:

  "URL:http://abc.com/pub/calendars/jsmith/mytime.ics"
  "URL;VALUE=URI:http://davidcrow.ca/"
  "URL:http://host2.com/pub/busy/jpublic-01.ifb" (for a VFREEBUSY)


=head1 iCalendar Issues

Recurrence is complex, probably overly so.

The standard requires that timezones be defined inline, yet
there may be redefinitions of those timezones in the future
that even affect future dates in existing calendars.
This can mean conflicts with the conventional definition
of the same-named timezones. This could happen with distant
future events in old calendars,, as well as recurring events
beyond a change in the definition.

The properties such as UID, DTSTAMP, CREATED contrast
"calendar store" with "object representation". This has unclear
meaning when objects might be reformatted, republished, and so on.
The semantics of references to other objects such as by RELATED-TO are similarly
confusing.

DTEND is unclearly defined.

Many properties could be used with different semantics, and in
some cases you'd like to use more than one such meaning at once.
For example: 

  is URL the authoritative ics file? a web page? a brochure?
  what about ATTACH? Note it can have a URI value also.
  (cv. WHURL and PROMO in SkiCal)

iCalendar is focused on business meetings (ATTENDEE property, SENT-BY parameter, etc.),
without a similar degree of support for public events.
For example:
  no distinction between event title and summary (SkiCal TITLE)
  no way to indicate a set of multiple performers/speakers (SkiCal PERSONS, SKiROLE)
  no way to indicate type of location (radio, TV, indoors, outdoors) (SkiCal VENUE)
  no structured way to specify admission information (cost, tickets, reservations, etc.)
     SkiCal ACCESS PRICE PAYMETHOD BOOKINGS PROHIBITED
  no way to indicate the languages spoken at the event (vs. language of text in description) (SkiCal SKILANG)
  no easy way to indicate a schedule within the event (SkiCal OPTIMESET)

It has weak support for alternate DESCRIPTIONs (html vs. text; short vs. long).
There is the ALTREP parameter, but it makes little sense outside of a MIME context that can provide additional attributes.
There is the LANGUAGE parameter which apparently allows for multiple LOCATION and DESCRIPTION 
and other text properties that otherwise can occur only once --
although the RFC is unclear on this, as 4.6.1 "eventprop" production says
that "the following are optional, but MUST NOT occur more than once".

There is no certain way of distinguishing an unknown time, an unspecified time,
and an all-day event. Or of saying "some day between may 1 and may 8".

What distinguishes COMMENT from DESCRIPTION?

The LOCATION is free text, with no structured address support such as with
vCard (place name, address, phone), nor a distinct directions field
(like SkiCal DIRECTIONS, PLACENAME properties; TRAVELBY parameter).

ORGANIZER is too limited as cal-address, and CONTACT is too free.
What if the real organizer is an organization with a title, phone, etc.?

There is weak and unclear specification for charsets: Can UTF-16BE be used?
What to do once a VCALENDAR is detached from a MIME container? 

There is no property for a VCALENDAR title (like X-WR-CALNAME) or the owning organization of a VCALENDAR.

Multi-user change tracking is weak (no distinction between submitted by, 
posted by, posted when, etc. -- each of which might differ from the organizer). 
SkiCal has PUBLISHER and MANAGEMENT, but those still don't really cover
it all either.

There is no suggested manner for namespace control on values of
enumerated properties and parameters (CATEGORIES property, RESOURCES property,
ROLE parameter, etc.) (see SkiCal NSREF).


=head1 Example Event

================================================================

Teaser
   Hear From a Courageous African Woman Who Stood Up 
   to the Vicious Ethnic Cleansing of the Black Community of 
   Tampa, Florida -  and Won!
 
Title:
   "Is the San Francisco Bay Area for Whites Only? A Forum on Ethnic Cleansing"

Subtitle:
   with housing community activist Connie Burton from Tampa, Florida

When: 
   Tuesday, June 29th,  7 to 9:30pm

Where: 
   Fellowship Hall of Humanity, 390- 27th St., ( between Telegraph and Broadway), Oakland

Contact: 
  African People's Solidarity Committee, (510) 295-7834
  Call (510) 295-7834 for more info, leave a voicemail at 510-625-1106, or email uhurureparations@yahoo.com

Description:

On this coming Tuesday, June 29th from 7 to 9:30pm, the African
People's Solidarity Committee is holding "Is the San Francisco Bay
Area for Whites Only? A Forum on Ethnic Cleansing" at the Fellowship
Hall of Humanity at 390 - 27th St (between Broadway and Telegraph) in
Oakland.

Featured as the keynote speaker will be Connie Burton, leader in the
International People's Democratic Uhuru Movement out of Tampa,
Florida.

Several months ago, Burton led an African community struggle against
the city of Tampa's plans to kick African people out of the Tampa Park
apartments in what the city considered "prime real estate."

Utilizing the combination of her weekly "Straight Talk" radio program
she hosts in Tampa with massive leafleting, bullhorning, protests and
participation in weekly Tampa housing authority meetings, the Uhuru
Movement in Tampa under Connie's leadership was able to push out the
city's latest ethnic cleansing plan to remove black people from the
neighborhood!

Join this discussion about the devastating situation that exists from
the Tampa Bay to the SF Bay as African people are forced from their
communities. Through policies of police containment and a U.S.-imposed
drug economy, young Africans in their communities in the Bay area face
prison, the military, or the grave while people people are able to
move into their neighborhoods.

Other speakers at the forum include:
 Quetzaocelocuia of the Barrio Defense Committee in San Jose, 
 Maurice Campbell of the Community First Coalition of Bayview-Hunter's Point, 
 Bakari Olatunji of the International People's Democratic Uhuru Movement in Oakland, 
 Wendy Snyder of the African People's Solidarity Committee.

Let's take a stand from the white community to support genuine economic development and an end to the war on the African community!

Brochure:
  download the leaflet at http://mrwillis.crosswinds.net/Leaflet_Uploads/Gentrification.pdf

=head1 Proposed Schema

Here is a proposed schema.
We attempt to indicate here the mapping of field(s) between our schema,
iCalendar, and Atom.

 Area
 When                
       when_start    DTSTART, @TZID
		     ISO8601 datetime with any precision (year down to second)
		     has a numerical tz offset, unless "floating".
		     offset taken from @TZID param, which is a name
       when_duration DTEND, DURATION
		     (we use duration instead of end to avoid extra rules about tz etc.)
		     if missing, then it is considered unknown (vs. 0 duration)
		     cannot have more precision than start
       when_recur    RRULE, EXRULE, RDATE, EXDATE

 Where               LOCATION (multi-line plain text)
		     whole location might be stored internally
  where_name	     single line free text 
  where_addr_pobox   the 7 vCard ADR fields; pobox and extended probably not used
  where_addr_extended
  where_addr_street
  where_addr_city
  where_addr_province
  where_addr_postal
  where_addr_country
  where_phone
  where_url          URL, home page for location
  where_directions   type=content (might be a link to directions)
  where_geo          GEO (two floats long/lat)

 What
		     all content fields can have content-type and lang
  summary            SUMMARY
		     type=content
		     in iCalendar, free plain text, typically single line.
		     used in isolation of rest of info. defaults to title, then to beginning of description
  title              -
		     if a movie, etc. that has a distinct title. will be shown in quotes.
  subtitle           shown with the title, should not be set without it
  description        DESCRIPTION
		     type=content
		     in iCalendar, multiple lines of free plain text which
		         includes all people involved, and any schedule
  link*              ATTACH, URL
		     RFC2445 URL;VALUE=URI could be either the event or an ICS; it is vague
		     attributes: rel href type (like Atom and HTML. Atom defines rel to be a URI or one of several tokens. type is media type here, and Atom says content/@type is broader)
		     		 HTML says rel is CDATA, space-separated: http://www.w3.org/TR/REC-html40/struct/links.html#h-12.3
		     rel="eventhome" "flyer" "brochure" "registration"
		        eventhome = a html home page specifically for the event (vs. typically pdf for flyer)
		     
  category*          CATEGORIES
		     exactly the same as Atom: term (text) label (text) scheme (URI)
		     	     no restrictions on term: http://www.atomenabled.org/developers/syndication/atom-format-spec.php#rfc.section.4.2.2
		     (alternative designs: URIs, TOKENs, QNames, labels)
		     TBD: namespace declaration, and schema of choice labels (SkiCal NSREF is unspecified what the URI points to)
		     one or more from various vocabularies
		       event_type: concert, movie, art (poetry, dance, painting), conference, 
			 forum, educational/training,protest(march,vigil), group meeting, 
			 fundraiser, social (celebration, etc.)
                       topic: police,prisons,education,health,democracy,
		        human rights,environment,homelessness,international economy,history,law,race,labor,drugs
		       incident: Katrina
		       geoname (which it is about, not held at, such as from Getty or usgov Metropolitan Statistical Area): Iraq,Africa
		       	       http://www.getty.edu/research/conducting_research/vocabularies/tgn/
		       	       http://geography.about.com/cs/largecities/a/metromicro.htm
  admission          tickets, reservation, price, etc.          

 Who                 ORGANIZER, CONTACT
  organizer_name     organization name or individual name
  contact_name       specific individual to contact
  organizer_email  
  organizer_url      home page
  organizer_phone

 Changes             CREATED LAST-MODIFIED UID URL
  created_by
  created_date
  source_url         original ics 
  last_modified 

Some come from a fixed vocabulary of choices:
  
  event_type
  topics
  
Some would be fkeys to a separate "address" table:

  location
  contact
  organizer

  full_name
  street
  street2
  city
  state
  postal_code
  country
  directions
  phone
  mobile
  email
  homepage

================================================================

=head1 RDF Calendar

RDF model for iCal: http://web.resource.org/rss/1.0/modules/event/
    notes that date precision is significant

more RDF and iCalendar: http://www.ninebynine.org/RDFNotes/Calendaring/iCal-proposal.html

http://esw.w3.org/topic/RdfCalendarDocumentation

http://swordfish.rdfweb.org/discovery/2003/11/rdfical/www2004-draft-20031113-final.html
        RDFiCal: iCalendar in RDF

http://www.w3.org/2001/sw/Europe/200404/rssical/rssical.html
        RSS and RDF iCalendar

http://www.w3.org/2002/12/cal/
        RDF Calendar
        ical2rdf.pl now replaced by fromIcal.py
        has tools to convert schema from rfc to rdf/owl
        Dan Connolly

http://dublincore.org/2003/12/08/dctype#Event
        dulbin core "Event" type DCMI



=head1 SkiCal

http://swordfish.rdfweb.org/people/libby/rdfweb/skical/skical-daml.daml
http://swordfish.rdfweb.org/people/libby/rdfweb/skical/skical-daml-diary.txt
        iCalender/skical in DAML+oil
http://skical.metamatrix.se/
Structured Knowledge Initiative
http://skical.metamatrix.se/skical20010905.html
http://xml.coverpages.org/draft-many-ical-ski-06.txt
        (defunct?)
        better suited for public (non corporate events)
        SkiCal - an extension of iCalendar
        adds WHAT,WHEN,WHERE,WHOW,WHY,WHO
        SKIROLE
        OPTIMESET opening time set
        OPTIMES
        TITLE (of the movie, etc.,, vs. SUMMARY)
        PERSONS (performer, presenter, etc.)
        CONTROL
        MANAGEMENT
        DIRECTIONS
        PROMO
        PUBLISHER
        WHURL url associated
        VENUE
        PLACENAME
        PRICE
        PAYMETHOD
        BOOKINGS
        ACCESS[ibility]
        NAMESPACE


=head1 Libraries

  perl
    ccal http://www.dns.net/dist/ccal-1.6
      (uses its own quick and dirty parser)
      GPL
    http://www.simondobson.org/downloads/files/ical2vcal
      iCal (v2) to vCal (v1) converter, using Text::vFile
    Icabra http://isg.ee.ethz.ch/tools/isgtc/index.cgi?page=module_source;module=icabra;source=icabra
      GPL 
    ical2rdf.pl http://www.w3.org/2002/12/cal/ical2rdf.pl
      W3 license. iCal convert to RDF. see also fromIcal.py 
    jclark on the perl modules: http://jclark.org/weblog/Programming/Perl/priorart.html



  python
    http://labix.org/python-dateutil
    http://vobject.skyhouseconsulting.com/svn/vobject/parsing.py
      vobject  Apache license vobject
    http://svn.plone.org/view/collective/Calendaring/trunk/parser.py?op=file&rev=10643&sc=0
      GPL.
    http://codespeak.net/icalendar/
      LGPL
    http://distfiles.master.finkmirrors.net/ccal041.py
      GPL curses calendar manager
    http://www.w3.org/2002/12/cal/fromIcal.py
      W3 license. iCal convert to RDF. see also ical2rdf.pl
    http://sourceforge.net/projects/collective http://plone.org/newsitems/ploneicalendar/talkback/1087233044
      Plone implementation.

  Erlang
    http://www.stacken.kth.se/projekt/yxa/cpl_implementation.html

  Java
    http://recurrance.sourceforge.net/
      Apache license. implements RRULE
    http://wiki.osafoundation.org/bin/view/Journal/JeffreyHarrisToDo
      who can say.
    http://ical4j.sourceforge.net/
      MIT license. parser.
    http://co-project.lboro.ac.uk/users/coch2/jical-1.4/docs/html/
      JiCal. LGPL. iCalendar to html

  C
    http://dev.w3.org/cvsweb/Ical2html/
      W3 license. C. iCalendar to HTML. uses libical.
    libical http://www.softwarestudio.org/libical/ and http://www.aurore.net/projects/libical/
      LGPL/MPL
      libical-0.24 (Nov 24) was last release
      being picked up at http://www.aurore.net/projects/libical/
    http://korganizer.kde.org/develop/architecture.html
      libkcal is C++ wrapper around libical
    http://cvs.gnome.org/viewcvs/libmimedir/mimedir/ 
      LGPL parser. handles vCard, vCal, iCalendar.
      not to be confused with http://sourceforge.net/projects/libmimedir/
      maintained by Sebastian Rittau <srittau@jroger.in-berlin.de> 

  Ruby
    http://icalendar.rubyforge.org/
    http://vpim.rubyforge.org/
    http://www.infinitenil.com/developers.html http://www.macdevcenter.com/pub/a/mac/2003/09/03/rubycocoa.html?page=last&x-maxdepth=0
    http://noir.s7.xrea.com/pub/zaurus/ics2csv.rb
       GPL ruby converts ics to a CSV 

  Objective C
    http://svn.opengroupware.org/SOPE/trunk/sope-ical/iCalSaxDriver/README
        LGPL. objective C. parser of iCalendar. for converting icalendar to sax parse events corresponding to xCal.

  C#
    http://remotecalendars.sourceforge.net/
      COM plugin for Outlook
    http://sourceforge.net/projects/icalparser/
      GPL C# primarily to convert to RDF

  PHP
    http://www.k5n.us/webcalendar.php?topic=FAQ
      WebCalendar
    http://cvs.drupal.org/viewcvs/drupal/contributions/sandbox/thehunmonkgroup/eventrepeat/eventrepeat.module?view=markup
      drupal module
    opengroupware
    http://dev.wp-plugins.org/file/ical-events/trunk/import_ical.php
       wordpress plugin

  Lisp
    http://de.geocities.com/ulf_jasper/lisp/icalendar.el.txt

=head1 Perl Modules

perl cpan support
     problems with cpan iCalendar modules at http://jclark.org/weblog/Programming/Perl/priorart.html

DateTime::Format::ICal http://search.cpan.org/dist/DateTime-Format-ICal/lib/DateTime/Format/ICal.pm
        part of the latest datetime.perl.org project
       Dave Rolksy
       adopted from Date::Ical
       will parse recurrence (also uses DateTime::Event::ICal)
DateTime::Event::ICal http://search.cpan.org/dist/DateTime-Event-ICal/lib/DateTime/Event/ICal.pm
        part of the latest datetime.perl.org project
      Flavio Soibelmann (also author of Date::Set, which became DateTime::Set)

Net::vFile http://search.cpan.org/~jlawrenc/Net-vCard-0.5/lib/Net/vFile.pm
        vCard and vCalendar

Text::vFile
   does not expand RRULE. does not support nested structures.
   same author as Net::vFile; no work since 2003.
   no writing

Date::ICal http://search.cpan.org/~rbow/Date-ICal-1.72/
           by Rich Bowen and the Reefknot team
           parses either ISO8601 or an ical duration
           no recurrence

Net::ICal http://search.cpan.org/~srl/Net-ICal-0.15/lib/Net/ICal.pm
	  no work since 2001; never finished.
          also part of reefknot
          supports rrule etc. at least in Net::ICal::Journal http://search.cpan.org/~srl/Net-ICal-0.15/lib/Net/ICal/Journal.pm
          which creates Net::ICal::Recurrence

Text::vFile::asData
   does not expand RRULE. does support nested structures. does not unescape \,

Date::Set http://search.cpan.org/~fglock/Date-Set-1.30/lib/Date/Set.pm
        can combine multiple dates.
        has internal support for Date::Set::ICal
        also part of reefknot
        supplanted by http://search.cpan.org/~fglock/DateTime-Set-0.17/lib/DateTime/Set.pm

iCal::Parser::HTML
     uses iCal::Parser::SAX uses iCal::Parser uses Text::vFile::asData and DateTime::Format::ICal

iCal::Parser uses Text::vFile::asData.
   It does expand RRULE, using DateTime::Format::ICal->new()->parse_recurrence 
   It also expands events spanning multiple days into individual events.

Data::ICal
   Artistic license. by Jesse Vincent, David Glasser, Simon Wistow
   uses Text::vFile::asData to parse.
   does its own writing. 
	


=head1 Open Source Native Clients

Rainlendar http://www.rainlendar.net/ http://www.ipi.fi/~rainy/index.php?pn=projects&project=rainlendar
	   Windows only client
	   server runs windows or linux
	   its own protocol not caldav. uses http://ssobjects.sourceforge.net/
	   GPL C++


Chandler

Mozilla Sunbird (win32, osx, linux)
   http://www.mozilla.org/projects/calendar/sunbird_download.html
   only does webdav, not RFC protocol (as implemented by Sun)

Evolution http://www.novell.com/products/desktop/features/evolution.html (osx, linux)
        Evolution Calendar "based on" GnomeCal, gnome calendar part of evolution
              worked on by "Frederico"
              Russell Steinthal rms39@columbia.edu interested in it http://www.softwarestudio.org/non-vc/MailArchives/libical/0165.html
	  was: http://www.helixcode.com/apps/evolution.php3 http://primates.helixcode.com/~miguel/activity-log.html

KOrganizer http://korganizer.kde.org/ (win32, osx, linux)
        does vcalendar
        http://devel-home.kde.org/~korganiz/development.html#architecture

Kalendar
        no client-server, vcalendar, etc.

http://www.gnome.org/users-guide/gcal.html
        uses icalendar
        http://www.gnome.org/mailing-lists/archives/calendar-list/
        gnome-pim works with it?

        


=head2 Commercial Calendar Clients

30boxes.com
	web-based ajax editing
	supports ics export

Yahoo Calendar calendar.yahoo.com
   will take yahoo CSV export to produce ical: http://www.manastungare.com/projects/yahoo2ical/

Microsoft Outlook
	  has problems: http://sippey.typepad.com/filtered/2004/02/ical_and_outloo.html

http://www.rockinsoftware.com/WinDates.aspx
	shareware, now withdrawn

http://www.even-t.com/even-t.html

CorporateTime http://www.cst.ca/ -> www.steltor.com -> Oracle
        enterprise calendaring and resource scheduling
              has linux support
              spun out lexacom then brought it back in
              had some of the original tech in Netscape CS?
              on icalendar committee
              Lexacom/Corporate Software and Technologies (CS&T)
              montreal canada

=head1 Web-Based Clients

lists and reviews:
  http://planscalendar.com/index.php?p=competition
  http://www.machineofthemonth.org/articles/2003/0324/index.html
  http://courses.washington.edu/~hs590a/modules/23/webcalendars.html
  http://www.mg.co.za/mg/pc/9904/21apr-webcalendar.htm

software: PHP iCalendar
          home=http://phpicalendar.sourceforge.net/nuke/
          home=http://phpicalendar.sourceforge.net/phpicalendar-0.9.4/day.php
          home=http://sourceforge.net/projects/phpicalendar
          language=php
          license=GPL
          description=<<EOF
example use at http://calendar.resist.ca/month.php
no editing, just presents a .ics file
demo at http://phpicalendar.net/phpicalendar/
parser is limited: doesn't even deal with escapes!
fork to support booking, at http://www.nanofab.ualberta.ca/iCalDemo
	discussion at http://phpicalendar.net/forums/archive/index.php/t-1126.html
	http://www.nanofab.ualberta.ca/phpiCalDistro.zip
EOF

Monket Calendar http://www.monket.net/wiki/monket-calendar/
       GPL/CC dual license
       php + ajax
       author taking a break

"UW Calendar" http://www.washington.edu/ucal/
  bsd license. java xml xslt.
  implements caldav
  ambitious
  currently no recurring support
  looks good; see: http://events.rpi.edu/showMain.rdo;jsessionid=EDB0054633915C25C6890443A7A13106
	and http://berlin.ucs.mun.ca/java/cal/

http://planscalendar.com/
      perl GPL
      demo at http://planscalendar.com/demo/
      has web-based create.
      decent look.
      themes, translations, plugins
      some recurring support.
      has export to vCalendar not to iCal
      will import an ics file: http://www.planscalendar.com/forum/viewtopic.php?t=1091
      but not yet modify an ics: http://www.planscalendar.com/forum/viewtopic.php?t=612
      stores data in flat files or in database
      some massive perl files with intermixed html, etc.
      has its own parser

iCal::Parser::HTML
        Perl license. demo?
	includes ical.cgi that is a cgi for displaying ics files
	http://cpan.uwinnipeg.ca/htdocs/iCal-Parser-HTML/README.html

http://jwebcalendar.sourceforge.net
	java. uses xslt and javascript.
	seems dead

http://dev.neb.net/phpMyCal/
	works with phpicalendar, gets ics out of mysql
	no updates since 2004

webcalendar.sf.net = http://www.k5n.us/webcalendar.php
          php GPL. uses mysql.
          has web editing
	  exports to iCalendar or vCalendar
          demo at http://www.k5n.us/opensource/month.php
          can act as a "calendar server" for Mozilla Sunbird or Apple iCal.
                a fork is used by pgw.
                exports iCal
                lists others at http://www.k5n.us/webcalendar.php?topic=Competitors

WebCalendar  http://www.math.utexas.edu/users/mzou/WebCalendar.html
       mod_perl  GPL
       has translations to many languages
       not that great looking ui by default
       has a "calendar server" (its own http post mechanism)
       "drag and drop editing"
       supports vcs files (not ics?) 

extcal  http://sourceforge.net/projects/extcal
           php GPL mysql
           no iCal?
           demo at http://www.maroctour.com/cal/calendar.php
           looks great
	   has web-based create
	   formerly EXTcalendar http://www.realize.be/swentel/module.php?boxcontent=5&boxid=4


http://sourceforge.net/projects/iwebcal/
	now commercial service (2003)
                php GPL
                from http://www.designtheworld.com/iwebcal/

http://sourceforge.net/projects/myxcal
	perl GPL
	uses xCal XML and XSLT
	nothing since 2003

http://myphpcalendar.sourceforge.net/
	abandoned?
        GPL php
        integrated with thatware.org

webcal http://bulldog.tzo.org/webcal/webcal.html
       went commercial in 2003 with http://www.webcalng.com/
       old sources at http://sf.net/projects/webcal/

http://www.circulargenius.com/flatcalendar/
                FlatCalendar no database. php

http://www.osafoundation.org/
    Cosmo is a calendar server (works with webdav/caldav client like Chandler, Apple iCal, Sunbird)
      apache license. java. requires maven, tomcat, etc.
    Scooby is a web-based client that will work with Cosmo (or any caldav server).
      jsp
    Chandler is a native calendar client
              python GPL. wxPython

=head1 Perl Modules for Generating Calendar HTML

PlotCalendar http://www.ajackson.org/software/plotcalendar/
	     perl module for generating html or ascii calendar display
	     will do Day or Month
	     little action since 1999

Calendar::Schedule http://users.cs.dal.ca/~vlado/srcperl/
		   still worked on in 2005

HTML::Calendar::Simple 
       2002
       simplified module inspired by HTML::CalendarMonthSimple.

=head1 Calendar Repositories

http://pax.protest.net/event.cgi?ID=480818&state_values=SITE!.40
	City & State
	Topic / Issue
	Location
	Speaker
	Phone Contact
	Sponsor
	Description
	Tube/Bus directions
	Contribution

http://events.moac.org/

http://www.radicalendar.org/index.php?function=subscribe


=head1 Commercial Hosting

http://www.icalshare.com/
   uses phpicalendar
   allows export
   no online authoring - in fact doesn't host at all, but pulls ics files from somewhere else

http://upcoming.org/

http://www.planzo.com/

http://icaldates.com/
	affiliated with http://www.rockinsoftware.com/WinDates.aspx

http://my.calendars.net/bsupcalendar/d01/10/2005?style=B&display=M&positioning=A
        pay for no ads
        works with iCal
        no export

=head1 Implementation Notes

In javascript you can figure out what the client's timezone offset is
         var now = new Date();
         //  ( 0 - LocalTZA - DaylightSavingTA(t)) / 60000
         var tz = now.getTimezoneOffset(); // GMT - local time. so positive number in USA.

=head1 Old Unsorted Links

html calendar in perl : http://www.mattkruse.com/scripts/calendar/download/

another calendaring: http://www.ecal.com (does it for other web sites)
        60% share: zdnet, cspan, sportsline, dejanews, infoseek

        ecal was formerly appoint.net (changed feb 99)

web calendar: http://www.boutell.com/calendars/

http://www.redhat.com/news/freshmeat/index.html#WebCal11


nice looking web calendar (from the imc product listing): http://www.softimage.com/default.asp?url=/events/default.asp

http://www.gallanttech.com/resources/documentation/calendar/
        mod_perl, gpl
        not a great ui (small, black)

HTML::CalendarMonth http://www.mojotoad.com/sisk/projects/HTML-CalendarMonth/

http://www.neosystem.com/wcal/
        GPL
        perl

http://www.extropia.com/hacks/webcal_all.html
http://www.extropia.com/scripts/calendar.html
        last done in 98. now at http://www.perl.jann.com/ -> http://www.calendarplus.com/index.shtml
        webcal

webevent http://www.webevent.com/ http://freshmeat.net/news/2000/10/11/971260145.html
         open source commercial perl

www.webcal.com -> http://calendar.yahoo.com/

http://www.radix.net/~cknudsen/webcalendar/
        php

http://mkruse.netexpress.net/scripts/calendar/docs/
        perl. unclear license

http://www.blue-gecko.com/framecal/
        perl.

http://www.efridge.com/?userhash=demonstration
                commercial web-based
                personal and public

citadel http://uncnsrd.mt-kisco.ny.us/citadel/
                multi-protocol BBS

framecal http://curiosityshoppe.tierranet.com/framecal/cal.html
                 web-based service

http://www.cp.net/solutions/cal_ec.html

software: Lozinski's Calendar
        topic=web calendars
        home=http://www.davelozinski.com/scripts/calendar/
        license=commercial

http://www.schipul.com/tendenci/calendarevents/event_admin.asp
        commercial
        Tendenci

http://www.kamath.com/calendar/
        ASP
        license: no-redistribute, must-link: http://www.kamath.com/calendar/copyright.asp
        dead since about 1999
others