The Time Rings (時の指輪 Toki no Yubiwa) are an accessory for the Supreme Kai to be able to travel through time.
The Time Rings have several special abilities, unlike the Time Machines created by Capsule Corporation, the Time Ring allows for "natural" time travel, and so does not create alternate timelines when used. Additionally, a wearer of a Time Ring will be granted a causality, and so even if their past were to be altered somehow - they would not be affected, as shown with the case of the Zamasu of the main timeline, as while he was killed by Beerus due to Future Trunks altering the timeline, he still continued to exist with his unaltered history thanks to his Time Ring.
It had been said that the Time Ring were used and only worn by the Supreme Kais who often used them to travel through time. A Potara earring is required in order for anyone to use the Time Ring, as explained by Gowasu.
Green time rings represent the creation of alternate timelines. Thus, the number of green rings indicate how many people have traveled into the past. A new ring is created whenever another person modifies the past. There are 4 green time rings and 1 silver one implying there are 5 timelines, however it could be that the silver time ring is the one for the timeline it came from, while the green rings are possible timelines one can travel to. So the silver ring can travel to the timelines of any of the 4 rings (Timeline 1, 2, 3, and 4). Meaning there are actually only 4 timelines.
The Time Ring is reactive to a disturbance in time that has been recently altered by an individual. Once the Time Ring is activated, a warp is created in the form of a dark portal, allowing the user to travel between past, present and/or future altered destinations for a short period of time, before the distortion in time and space returns to normal, pulling the user back to its original plane, sealing off that era of time.
Goku Black used the power of the Time Ring to find Future Trunks in the present timeline after he escaped using his Time Machine, but could only stay for a small amount of time before being forced back. Black only managed to go back in time because the Time Machine's journey into the past created a distortion in time and space which the Time Ring reacted to and opened a portal into the past era.
According to Whis, the Time Rings are only used to travel to the future and then return to the present. Using the ring to travel to the past should be theoretically impossible and the user cannot travel back through time on their own free will. Also, only the Supreme Kais are allowed to wear them.
Unlike mortals, Gods can be affected by changes in their timeline. According to Beerus, killing a god in the past would cause that god to be dead in that timeline. Goku Black is the Zamasu of the same timeline in which he was killed by Beerus in the present, but due to wearing the Time Ring he was unaffected by changes in the past. Future Zamasu was the Zamasu of Future Trunks' timeline so he was not affected by present day Zamasu's death.
- The ring possess an infinity symbol almost identical to that of the Time Breakers' logo.