For discussion: should we return DateTime or DateTimeImmutable?

[g105b]

$dateFrom = $input->getDateTime("date-from");

What type of DateTime should this library return in this case? I like the simplicity of DateTime, and with it being a getter it probably doesn't matter about immutability of the object itself, but would it make more sense or would it potentially confuse someone if the returned object was DateTimeImmutable?