When it comes to invalid date objects e.g. when using new Date() with an invalid date string, the stringify function throws an error.

See the example here:
https://svelte.dev/repl/db77cddd51d84149b7ddb9ce29a87ec0?version=3.49.0

But the same input does not throw an error when using the uneval function.
I guess it makes sense to have a consistent behavior there.

A solution to this problem could look like this:

// https://github.com/Rich-Harris/devalue/blob/master/src/stringify.js#L68
case 'Date':
	const isValidDate = !isNaN(thing.getDate())
	str = `["Date","${isValidDate ? thing.toISOString() : ''}"]`;
	break;

This gets rid of the error and when using parse you'll get back an invalid date.

What do you think?
I can submit PR if you want.