The site I'm working on right now was originally hand-coded 25 years ago, and then I rebuilt it on D5/6 almost 20 years ago. At that time, nodes didn't have an editable authoring time or even date fields, IIRC. Since the nodes were being imported, I wanted to save the original create dates, and so used a text field to store that info.
Now that (in Backdrop) I have the option to set Authored on if needed, I would like to transition over the old nodes to use that field and remove the custom field so that users don't have to enter the date for new content of the same type.
Any suggestions on how to do this programmatically for a bunch of nodes?