This tutorial will show you how to add multiple calendars to your your primary calendar. You can create as many calendars as you want.
Step 1: In Webmail go into Settings menu on the left
Step 2: In the middle pane, click Calendar Settings
Step 3: In the right pane:
1) Click the Calendars tab
2) Click the Add button
Step 3: You will see this pop-up window (below).
1) Enter a name for the calendar. In this example, we are naming it "Personal".
2) Choose a color to distinguish this calendar from others.
3) If you want to use the default blue color, put a check mark in this box.
4) Click Save
Step 5: You will now see your new calendar listed.
Rrepeat the previous steps to create additional calendars.
When you are finished, click Save
For more information on viewing multiple calendars: Click Here