Note: These instructions were made using Chrome. 

1. First, go to the settings icon in the top right corner.
2. In the search box start typing publish and select Publish a calendar.
    
   
   
   
3. On the right side of the page, look for Publish a calendar and select the calendar you want to export.  Select permissions, choose Can view all details and press Publish.
4. This will give you two options, HTML or ICS.  If you want to download the calendar, click on the ICS link.  This will open show a window prompting you to Copy link or Download.
5. Select Download. 
   
   
6. Go to your download folder and you can upload or import it after that into another app or service.