More Details About iCalendar
The IETF defines three RFCs for calendaring and scheduling: 2445(iCal), 2446(iTIP), and 2447(iMIP). ScheduleWorld provides an implementation of these three RFCs which build the foundation for interoperability between products. All calendaring and Scheduling applications available today are either using these standards, or are migrating to use them.

Outlook
A lot of work has gone into Outlook interoperability over the years. A quick Google search on "outlook interoperability" shows ScheduleWorld as the first link behind Microsoft (Feb 2005). Working perfectly with Microsoft products is very important and all Microsoft interoperability issues are given a high priority.

You can perform a simple bi-directional test by creating an event with an Outlook user as an attendee. You may have to create a new contact for the Outlook user. The Outlook user will see your new event as soon as the ScheduleWorld iCalendar email is received. You will see the Outlook reply if one is sent. NOTE: Only the Java client can handle replies at the moment.

Warning: Outlook only has the option to use open standards for meeting requests - not todos/tasks. This means you can not participate in group todo/task scheduling with people who exclusively use Outlook.

Mozilla Sunbird
The Mozilla Sunbird application is a standalone calendar application that can read and display (but not write) ScheduleWorld calendars. You can download Sunbird from here.

Yahoo!
ScheduleWorld used to be able to import/export the Yahoo! CSV format but something has changed and this no longer works. Hopefully this will be working again shortly.
You may have some luck if you export your Yahoo! calendar data, then open it in a text editor and page wrap the entire document. On Windows you also may need to go to format, font, and use Kern. The file may then import properly.

Google Calendar
This has been released in April 2006 and is being investigated for possible sync and ldap integration.

OS/X iCal
At this time (April 30, 2005) ScheduleWorld supports Apple's proprietary changes to the iCalendar specification and interoperates with iCal.

Evolution
There are no known issues with Evolution read-only subscribing to ScheduleWorld calendars.

WebDAV
Read-only WebDAV access is available. All ScheduleWorld users may enable calendar-specific WebDAV access in either public or password-protected mode via the preferences page.