If you use Outlook for your email and calendar, but also use Google Calendar (say one for business and one for personal), you can easily add your Google Calendar to Outlook so you can view all your calendars in one place.
Go to Google Calendar in your browser.
Log in to your Google account. You will need some information about the Google Calendar you want to add to Outlook for the initial setup in Outlook.
On the calendar page, click the arrow next to the calendar under My calendars and select Calendar settings from the drop-down menu.
In the Private Address section of the Details page that displays, click the green ICAL button.
The Private Address dialog box displays, showing you the URL for the selected Google Calendar. Select the URL and copy it by pressing Ctrl + C.
Open Outlook and click the File tab.
Click the Account Settings button on the Account Information screen and select Account Settings from the drop-down menu.
On the Account Settings dialog box, click the Internet Calendars tab.
On the Internet Calendars tab, click New.
The New Internet Calendar Subscription dialog box displays. In the edit box on the dialog box, paste the URL you copied from your Google account by pressing Ctrl + V. Click Add.
The Subscription Options dialog box displays with the URL displayed as the Location. Enter a title for the calendar, if desired, in the Folder Name edit box. You can also enter an optional Description. The check box under Update Limit is automatically checked by default. We left that setting as is. Click OK to accept your changes and close the dialog box.
Your Google Calendar is added to the list of Internet Calendars on the Account Settings dialog box. Click Close on the dialog box to close it.
The pane on the left side of the screen now lists your Google Calendar in addition to your Outlook Calendar. If you select your Google Calendar under Other Calendars in addition to the Outlook Calendar under My Calendars, both calendars are displayed side by side.
If you have multiple Google Calendars, you can add any of them to Outlook and view them when you want in Outlook without having to log in to your Google account.
No reason to reinvent the wheel. Google had, up until February 2013, an absolutely wonderful Outlook Calendar Sync app that worked seamlessly. I’ve been using it for a couple years and it seamlessly keeps the calendars on all my devices perfectly synced. Then Google removed this wonderful app at the end of February (along with a host of other free services), but stated that if you already had it installed it would continue to work. It does, perfectly.
What Google neglected to mention was that if you could still find the Outlook add-in, it would install and work just fine. Here’s the link Google Calendar Sync Outlook Add-in. Enjoy!
There is also an official app that syncs your calendar and contacts from Google to Ms Outlook here currently only for business users and not for free gmail users.
Another alternative is OggSync.