The mobile calendar can be filtered to selectively hide and show Plans and their associated Activities. This allows you to focus on up to three Plans at a time, while hiding other Plans that may be cluttering things up.

To control which plans are in view tap on the Filter badge, which will either say "All Plans" or "Filtered". This will take you to the Calendar Options. There, under "Applied Plans" you will see all of the Plans applied to your calendar, and the option to hide or show them, based on their current visibility.

Important Note: The calendar will display up to three Plans and their Activities at a time. If you have calendars with more than three Plans running concurrently, a red "Filtered" badge will be displayed (as shown above). This indicates that there are additional Plans and/or Activities applied within the timeframe you are viewing. To show them, tap into the Calendar Options and bring the hidden plan into view.

See here for a description of calendar filtering on the web.