What is the difference between "calm" and "sober"? Which word is more appropriate for "people should stay calm"?

calm: adj. (person, behavior or behavior) calm; calm; calm; (weather) windless

n. Calm; windless

v. To calm down, calm down; comfort

sober: adj. not drunk; sober

v. (to make) sober; (to make) sober

So calm is more suitable for "people need to stay calm": Stay calm