I had a shared a calendar my Google calendar with John Smith. John was able to view my calendar on his Google Calendar in the browser – but wouldn’t show up on his iPad and iPhone. I had to add my account onto his devices so he could see the calendar. But this way he could have access to my emails, contacts and all other google data. Therefore, I found this cool solution. John logged into his Google account on the web and used this URL to show list of shared calendars. John selected my calendar and it now shows up on his Apple devices without having my account on his device.