How to sync one calendar between two iPads?

I want to sync my wife's calendar with mine and wondered if there was an easy way to do this, thanks.

What email service or services do you use?

If you use Google or MobileMe, easy. I'm not sure about the others.

Both of us have gmail accounts.

No problem. Only one of you should do this step. Using the full Google web interface you need to create a new calendar. Just click on the Add link under the My Calendars lists. When you've named it and whatever notice near the bottom where it says share with specific person. Enter the gmail address of the other person, choose the share permissions you want, then click on Add Person.

At this point it might be a good idea for you to both experiment a bit with the calendar using the web site. Make sure both accounts can get to it and do what you want.

Once you're happy with that, you'll both want to delete your GMail account settings on the iPads and recreate them as Exchange accounts. Don't worry. All your stuff is on the server. You won't lose anything. [If you have a local calendar on the iPad with stuff on it, be sure not to overwrite the info when adding GMail again. Just choose wisely when you get the pop up notices.]

Use this method: Setting up Google Sync with your iOS device : Mail, Calendar, & Contacts - Google Mobile Help

When you've done that you'll only see your primary calendar, just like before. To see the new calendar you need to use Safari on the iPad to visit m.google.com/sync. Sign in if you need to, then select your device from the list. You'll see a list of your primary and shared calendars. Just check the one's you want to sync, then hit the save button.

Do this for each account.

You can sync just about any Google calendar you create or subscribe to this way. As a bonus you can also sync your Google contacts with this type of account.

There are several variations you could make. For instance, instead of making a new shared calendar, you could go to the setting for your main calendar and share it instead. If you both did this for the other person, and make those calendars view only, you'd be able to view each other's calendars while still keeping them separate.