Manually setting `_createdAt` field after creation time in Sanity.io.

Is there some way to manually set

doc._createdAt

after creation time? I ran a migration to import a bunch of Markdown docs last week, but sadly forgot to apply the original dates to this field.

I already have a custom

publishedAt

field that I can use for the patch

As far as I can tell though, _createdAt is read-only

Update: After some more searching it does seem like the

_

prefaced fields are readonly.
For future searchers who made the same mistake, here's what I'm doing to move forward:
• Made my custom

publishedAt

field

hidden

in my schema definition, so it will be undefined on all posts created in the future.• On my client, replaced

doc.publishedAt

with

doc.publishedAt ?? doc._createdAt

to account for old posts and future ones.