How do I hide my work, personal, holiday and other calendars on my iPhone calendar?

If you have several calendars synching with your iCloud Calendar it can get a bit crowded. You can easily hide other calendars by tapping the "Calendars" button at the bottom center. Now you can simply check off the ones you want to see and leave the ones you don't want to show unchecked. You can tap "Hide all" to hide all the calendars from an imported source like a Gmail calendar. Tap "Done" in the top right when you are finished.