Some considerations in choosing a plugin or script to import one or more shared calendar ical feeds:

• Completeness and/or robustness of ical implementation? vs type of dates expected by your application. A complete implementation may of necessity be more complex than a simple one. If your dates are simple, may be a simple solution is the answer. Or do you need to allow for all the variations of recurring specifications?
• Does it cater for all the fields you need? (attendees etc….)
• Box Calendar or List of Events (Agenda Style)
• Verbose or concise text (eg: Mo, Tu vs Monday, Tuesday)
• Explanatory Text options to change?
• Hardcoded english? or are there language translation options?
• Possibilities for css styling – does the html code produced allow adequate styling opportunities?
• Caching? If you have a high volume site, or you want the calendar or agenda in your sidebar, then you need to cache the ics file to avoid placing too much of a load on the server that is hosting the ics file (and slowing down your site)
• Can it handle or combine multiple calendars?
• Will it repeat the recurring events per day? or does it note the fact that they repeat on the first day or the current day?

Resources

• A google test calendar with a variety of recurring dates (note since singled events will drop off the calendar, you may want to create your own test calendar, importing these test events if you wish. Use this URL to download the ics file: http://www.google.com/calendar/ical/i9o399hd2c6bvgbch9oa6misc0%40group.calendar.google.com/public/basic.ics
• ICAL specifications
  • http://www.ietf.org/rfc/rfc2445.txt
  • http://en.wikipedia.org/wiki/ICalendar
  • http://www.kanzaki.com/docs/ical/
• PHP date specifications (used by many plugins to allow customising the date and time formats

WordPress Ical (ics file) import options:

These are ‘old’ – please see http://webdesign.anmari.com/95/comparison-of-event-calendar-plug-ins/

• http://wordpress.org/extend/plugins/wordpress-ics-importer/ This one looks good, not a full implementation of the code, but the code that is there is well structured, allowing for additional implementation in a clean fashion. Provides a cache. No language translation and alternative css and html options are possible, but not that obvious or easy until you dig into the code. One calendar at a time.

• http://webdesign.anmari.com/icalevents-table/ an off shoot of the next one Adam Gordons, but with alternative html layout and additional css tags for custom styling, etc). Working on translation and additional formatting options, and a standalone test. Both handle multiple calendars.
• http://webdesign.anmari.com/web-tools/plugins-and-widgets/ical-events-list/ Better version of the above (more robust, more styling, still not repeating, but may be adding that soon).
• http://wordpress.org/extend/plugins/ical-events/ Well written, handles a fair bit of the Ical Spec, could use a layer of “wordpress presentation” ie plugin customisation page and widget.
• http://www.xvx.ca/icalevents/ (Adam Gordons) , No cache. Hardcoded English. Offers a
• http://code.google.com/p/wpng-calendar/ and some info on using it. Has a widget option.
• http://wordpress.org/extend/plugins/upcoming-events/#post-315 Does not handle recurring events. Has cache, and can handle multiple feeds. Has a widget option.