It's possible if he makes you a delegate or gives you the proper
permissions.

Hello,

It is possible however, it depends on the permission level you were assigned
by your boss. For example, I can give you the author level and therefore you
can change my current appointments etc. Do you have permission to use your
boss's calendar? If so can you view your calendar and his/her as well? You
can also, drag and drop between calendars.

Hope this helps,
Patricia Orlic