Doctor Odd’s Laundry

Vinegar, ammonia, and hydrogen peroxide are three things you can use to remove bloodstains from clothes.
But for a famous mad scientist like Doctor Odd, such simple chemistry is beneath him.
Nor is he willing to waste time arguing with the corner laundry. Their prices are unreasonably high, and use too much starch.
Instead, he uses his time machine to return to a time before the blood stained his clothes.
But, by protecting his earlier self, his future self ends up with the bloodstains.
Dr. Odd shrugs, changes clothes, puts on a smock, and heads back in time once again.