Google Calendar for iOS is now available as a free download on the Apple App Store. Google Calendar for iOS lets you see your schedule with maps and photos of the places you're going. Information from Gmail like flight, concert, restaurant and hotel reservations are automatically added to your calendar.
Entering events can be accomplished quickly and easily, and you can switch between viewing a single day or multiple days. Google Calendar will work with the other calendars you have on your iPhone.
You can download the app directly on your iOS device through the Apple App Store or by using the following link:
Based on the reviews, it doesn't look like the initial release of Google Calendar for iOS supports landscape model. Hopefully Google will add this functionality in a future update to the app.