Apple introduced iCal - a new calendar program with built-in Internet sharing that lets business users, consumers and educators manage multiple calendars, share them over the Internet and automatically keep them updated – at Macworld Expo in New York.

Users can “publish” their iCal calendars on the web, so colleagues, friends and family members can “subscribe” and view them in iCal on their own Mac. Apple claims that single-window iCal can automatically check for updates to imported calendars on a regular basis, so shared calendars are always up to date.

“iCal lets you see all the calendars that make up your life,” said Steve Jobs, Apple’s CEO, during his Expo keynote speech. “With built-in Internet sharing, iCal opens a new era of wide-area calendar sharing between colleagues, friends, family and schools. It’s the best calendar ever seen in a computer.”

iCal will be available as a free download this September and requires Mac OS X version 10.2. Publishing calendars on the Internet requires a .Mac membership or a WebDAV server.

Multiple calendars in one window With iCal, Mac users can manage and view multiple calendars at once from within one unified window to easily identify schedule conflicts or free time at-a-glance, and publish calendars on the web to share with colleagues, family and friends. Users can send standards-based email event invitations, organize and keep track of activities with built-in To Do list management, and be notified of upcoming events on screen, by email or text messaging to a mobile phone or pager.

Apple’s new iSync allows users to sync their iCal calendars with the new generation of Bluetooth-enabled mobile phones, PalmOS devices and the iPod for access to their most current address books and calendars on the go.