You can do this by first exporting your Yahoo Calendar in the iCalendar (ICS) file format. You can then import that file to your Google calendar. Please take a look at this Help article for more specific instructions on exporting:
Exporting Yahoo Calendar to an iCalendar (ICS) file
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Hi Robert,
You can do this by first exporting your Yahoo Calendar in the iCalendar (ICS) file format. You can then import that file to your Google calendar. Please take a look at this Help article for more specific instructions on exporting:
Exporting Yahoo Calendar to an iCalendar (ICS) file
http://help.yahoo.com/kb/index?page=content&id=SLN...
Please let us know if you have any other questions.