How you use your Google calendar with Yahoo can synchronize, we show you in this guide.

Google calendar sync with Yahoo

Log in to Yahoo with your username and password and open the calendar Overview.
Click in the left margin on the Gear and select "Share".
Select the appropriate calendar and confirm with "Next".
Copy the iCal address to your clipboard. You can find the URL under "With iCal, and address as a Link to share".
Open the calendar Overview of Google and log in with your login details.
Click on the small arrow next to "Other calendars" and select "About add URL".
Copy the address from your clipboard into the link-field and confirm it. The synchronization may take a few minutes.