Ring of Borrowed Time

Ah, the Ring of Borrowed Time, you said as well? I'm well and truly sorry, I din't hear you at first. That's a fascinating artifact! This ring grants the wearer the ability to briefly turn back time, allowing you to correct a past mistake. It's a one-time-per-day use, where if things didn't go quite as planned, you can use the ring to try again. Quite handy in a pinch, wouldn't you agree?
Now, just like many powerful items, this ring comes with a bit of lore and legend. It was crafted by a dying wizard who sought to extend her life to escape a rapidly growing illness. Unfortunately, while she hoped to gain years, she only managed to buy herself a few fleeting seconds. The ring's power, you see, has its own... subtle demands. Time borrowed must eventually be repaid, though the manner of that repayment isn't quite clear.
It's a piece with quite a story, and one that requires a thoughtful owner.
Once per day, whenever you make an attack roll, an ability check, or a saving throw, you can use the ring to re-roll the die even after the result has been determined.