Decades: 20s BC 10s BC 0s BC 0s 10s - 20s - 30s 40s 50s 60s 70s
Years: 20 21 22 23 24 - 25 - 26 27 28 29 30
Births
Deaths
... for a variety of reasons: The placebo effect. Medicines or treatments, known to have no effect on a disease, can have major effects on a person's perception of their ...