If you have permission from another Gmail user, you can merger her Calender with your.

Steps to Merge another user’s calender:

  1. Obtain another user’s permission.
  2. Log in to your gmail account.
  3. Click on “Calender” on the upper right hand corner.000 - Access Google Calender
  4. Enter another user’s gmail address in the calender area (as shown).001 - Enter Calendar Owner email

That is it. It is easy if you know how to do it.