This article explains that it is no longer possible to sync Yahoo!7 Calendar with BlackBerry devices. Similar topics searched on include:

• I want to sync my calendar with my BlackBerry.
• Why won't my BlackBerry and calendar sync?

While syncing your Yahoo!7 Calendar to your BlackBerry may have worked in the past, this operation is no longer supported. If you are no longer able to sync your Blackberry to your Yahoo!7 Calendar, we apologize but we will not be able to assist you with this issue.

Yahoo!7 and RIM BlackBerry are currently working on a resolution to sync your Yahoo!7 Calendar to your BlackBerry; we do not currently have an estimated time on this resolution.

You can still access your Calendar from your mobile device using the Yahoo!7 Mobile Calendar page. To access your calendar, use your mobile browser to visit m.yahoo.com/calendar