Working with an attorney who handles a lot of divorces, one of the things I have noted is that, when a mixed marriage falls apart, suddenly religion becomes an important issue.  We've seen numerous cases where one of the parents suddenly insists they have to have parenting time on such-and-such days because of a religious obligation for Sunday services or Awanas or other events -- while the other parent points out they hadn't gone to mass for two years and oh, why shouldn't they have parenting time then because that's when their religious obligation is.