The following document explains how to change calendar view using an iOS device (iPhone, iPad, or iPod Touch).
iPhone Calendar provides multiple views of all visible calendars:
List View: Tap on Inbox at the bottom of the main iPhone Calendar display to see events from all visible calendars in a chronological iPhone Calendar list.
Day View: If a different day is being shown, tap on Today at the bottom of the main iPhone Calendar display to see a day view with events shown as time blocks, colored according to the color settings for the visible calendars. Otherwise, click on the day you'd like shown to bring up this view.
Month View: Tap on the month to see a view of the month with the current day highlighted. Each day with events will have a dot below the day number.
Year View: Tap on the year to see a view of the year with the current day highlighted. This interface is scrollable, so other years can easily be viewed.
A fifth view, similar to the Day view, automatically pulls up on the iPhone Calendar when you rotate the iPhone into a horizontal orientation. One will see the same type of display when one selects Day view, but for three continuous days. When in this view the regular buttons at the top and bottom of the iPhone Calendar display are not visible. Re-orient the iPhone to cause them to reappear.