In some Christian religions, very often baptism date is the only 'known' date and what is happening is this date is often used by users also in the 'Birth date' field. When working with profiles and adding new profiles (Quick add form), it will save a lot of time to have baptism date displayed wherever Birth date is found.
Visibility of both dates at the same time without having to 'drill' to another form would save a huge amount of time and effort and also help greatly with accuracy and usability, but is also critically important from a research and geneaology perspective.
In consideration of cultural differences and for users where baptism date is not relevant this would be best managed through a setup option (prefered as this is easier) or linked to the religion selected...