[jcparkyn]

If you know what modifications you need to make (hopefully the library author does), you only need to clone the relevant parts of the object (e.g. with spreading). Deep cloning still isn't usually necessary unless you're doing wierd stuff.

[qayxc]

The Date object would like to have a chat with you ;)

[jcparkyn]

I know you were mostly joking, but for cloning dates you can "just" use the constructor (https://stackoverflow.com/a/69601256).