This will be down to the permissions for each of the calendars.  

Whoever owns that calendar needs to set up the permissions for other users to be able to view the calendars. 

If you are the owner of a calendar then you can give other people access to the calendar in the following ways: 

Using the Manage Calendar button as shown below in red - users can select the following options: 

  • Do not share
  • Share with everyone
  • Share but hide all details
  • Share with specific people (other users)

Click on the Manage Calendar button as shown above in red where you will see the following options:

My Calendars:  This will list any calendars that are related to your user profile: 

Click on your calendar shown under My Calendars where you will see a details window for that calendar you have selected as shown below:

The Share with everyone: option is automatically set to share a calendar with everyone unless this has previously been changed.  

However you can change the settings by selecting:

Do not share or Share but hide all details from other users.

Just select the appropriate option and click on Save to update. 

You can also use the option Share with specific people: as shown below:

This works by typing in the persons name you wish to give specific permission to and then selecting from the drop down option the permission to:

When you have made your selection just click on the Add Person button.

Next click on Save.