Is it Possible to Sync calendars between 2 iphones?

My wife and I each have iphones (4s if that makes any difference). She syncs heres to her PC and I sync mine to my MBpro so we are not using the same computers to sync our iphones. Is there a way for use to sync the calendars between our phones so that she can see my schedule and i can see hers?

Thanks,

David