The Toki Toki no Mi is a Paramecia-type Devil Fruit that allows the user to send themselves and others forward in time. It was eaten by Kozuki Toki, but with her death, the fruit has returned into circulation.
So far, the only strength of the fruit is the user's ability to transport themselves or others out of dangerous situations by moving into the future. The user is also apparently able to decide the specific amount of time skipped for each trip.
It is impossible to travel into the past, meaning that all trips forward in time are irreversible. Otherwise, the user is affected by the standard Devil Fruit weaknesses.
During her life, Toki had used this ability to travel further and further into the future, allowing her to live in many different time periods. Whenever she found herself cornered by some apparent threat, Toki could activate her ability in order to escape it, moving forward to a time period where the threat was not present anymore.
At least 830 years ago, Toki ate the fruit and gained the ability to time travel to the future, having used the fruits ability to travel and live from one time period to the next, eventually landing herself 30 years before the present where she finally settled down and married Kozuki Oden.
She last used her ability to send her son and half of the Nine Red Scabbards twenty years in the future before her death, returning the Fruit to circulation.