June 2004

Open Dating

The open-source iCalendar standard allows people to coordinate their schedules.

By Simson Garfinkel

My lab at MIT publishes a calendar of events on its website. Lab staff can use the site to enter information about talks, seminars, and special events. Lab members can even sign up to get the day's announcements sent to them by e-mail. When I see a talk that looks interesting, I copy the announcement's text and paste it into my computer's calendar.

The registrar's office at MIT publishes the institute's academic calendar. This calendar tracks official events, such as the start of classes, institute vacations, and thesis deadlines for grad students. At the beginning of the school year, I spent half an hour entering these dates into my computer as well.

My wife, Beth, has a calendar, too-this one filled with doctor appointments for the kids, my daughter's gymnastics lessons, and the nights that I have child-care duties. She keeps her calendar on her Mac with Apple's iCal program and occasionally e-mails me reminders about important appointments. But she doesn't have to: less than 15 minutes after she enters an appointment into her calendar, it automatically appears in mine.

Like the MIT calendars, Beth's is also published on a website. But instead of being published in a form that's easy for humans to understand, her complete calendar is uploaded every 15 minutes in a computer-readable form called iCalendar. My calendar program downloads this file every 15 minutes and displays Beth's calendar events in a different color on my own calendar. Likewise, my calendar events are automatically uploaded to the Web server, downloaded by Beth's copy of iCal, and displayed on her calendar.

Don't confuse Apple's iCal program with the iCalendar file format: iCal is an application for the latest Macintosh operating system, but iCalendar is a six-year-old open standard that was developed to let desktop applications share calendar events. An iCalendar file can consist of a single appointment, a repeating appointment, or items from a to-do list.

Those same engineers who developed iCalendar also created vCard, a kind of virtual business card used to store names, phone numbers, and other contact information. VCard has become the standard for moving that kind of information around the Internet; you probably have received hundreds of e-mail messages with vCards attached. With most e-mail programs, you can just click on these attachments and have them automatically added to your address book.