any ideas on how to sync mine and my girlfriend’s iphone calendar’s? Help keep the family synced…?

My girlfriend and I live pretty busy lives and are looking to coordinate better. We both have iphones and have triend many programs on them to sync our calendars, contacts and such. None of the programs we've tried have worked. Does any one have any ideas for programs, websites ( like google calendar) that may help us. We do both already have google calendar but it doesnt seem to be ablye to sync both of us at the same time so one of us is always several hours behind. Any help is appreciated, thank you.