https://bigthink.com/starts-with-a-bang/...symmetric/
"One of the surprising facts about many of the laws of physics is that they're time-reversal-invariant (T-symmetric), meaning that particles follow the same rules whether you run the clock forward or backward. But there are certain symmetries that are shown to be violated, like replacing particles with antiparticles (C-symmetry) or replacing particles with their mirror images (P-symmetry). Since the combination of C, P, and T symmetries (CPT symmetry) must be conserved, violating CP implies that T symmetry must be violated, too. Here's how we finally showed that really is the case."
"One of the surprising facts about many of the laws of physics is that they're time-reversal-invariant (T-symmetric), meaning that particles follow the same rules whether you run the clock forward or backward. But there are certain symmetries that are shown to be violated, like replacing particles with antiparticles (C-symmetry) or replacing particles with their mirror images (P-symmetry). Since the combination of C, P, and T symmetries (CPT symmetry) must be conserved, violating CP implies that T symmetry must be violated, too. Here's how we finally showed that really is the case."