Hi Danny, Let's see if I have this straight. You learned of the name change from a family story, you have an oral history. This FAMILY ORAL HISTORY says your grandfather was born with the name Christensen/ Christiansen (rather than Hansen).
Your FAMILY ORAL HISTORY included your grandfather's parents names? What did the FAMILY ORAL HISTORY give as their names?
Your FAMILY ORAL HISTORY said your grandfather was born in Jutland. The man we are researching was NOT born on the peninsula of Jutland as far as I know. He was born in Sorø amt, yes? Sorø is on the same large island where Copenhagen is located.
Yes I can see Poul Erik Rasmussen is very reliable, I agree, but he was working with the information you gave him. You have a lot of confusing details to work with, and juggling all of it is not easy, I know, so let's double check how clear you are on what you told him.
That is why I think it would be great if you'd answer the above questions - and I don't mean to push you, just double checking here.
=================================== ABOUT DANISH NAMING PATTERNS
Usually when a FAMILY ORAL HISTORY says a Mr. Hansen was born with the surname Christensen, he is going to have a father named Christian or Christen.
In the olden days, a man called Niels Christensen would have children with the last name Nielsen (or Nielsdatter for girls). The children are "son of Niels" and "daughter of Niels."
Your grandfather was born at that time in history when Danesstarted to do as we Americans do. The children were given the same surname as their father. In this more modern Danish family, Niels Christensen's children would be named Christensen.
The decision about the surname was not necessarily made at birth. This generation of Danes made decisions as adults about what their permanent surname would be.
Usually a name gets changed when a person with an old-fashioned patronymic name switches to the modern way as an adult. Thus the children of Niels Christensen might be named Nielsen, but they would switch to Christensen.
=================================== You may know all this! But it's important to clarify that if Anton Laurits Christensen turned into Hans Peter Hansen, that is not normal Danish naming practice. The father of Anton Laurits is Niels, so we'd expect Nielsen as the alternate name, not Hansen.
That said, your grandfather was free legally to choose just about any surname he desired.