Drift can only connect directly with Office 365. Exchange, Exchange Online and Hybrid Exchange calendars will not connect. 
Here's how to set up your Office 365 calendar: 

1. Click the "Meetings" tab in the left-side Navigation Bar.

2. Choose Office 365 Calendar.

3. You'll be taken to a Microsoft landing page where you'll need to enter in your login credentials.

 

4. Click "Sign in" and you'll be good to go!

Note that your Office Calendar must be publicly hosted in order to integrate with Drift.

Remember, when you set up your calendar with Drift, site visitors have the option to schedule meetings with you directly from chat!