Out of the 3 billion years it is mostly a multitasking antioxidant. Sleep is only a small portion of what the molecule does.

I tried not to downvote your comments but "this molecule has existed for 3,000,000,000 years" is completely unrelated to whether it is a hormone — it is a hormone that is emitted by every normal human's pineal gland in the brain every night.

Whatever else it might be... you should stop.