Night is the time when the yogis remain awake." - Amma.

"At night the atmosphere is calm, for at that time
the birds, animals and worldly people are all subdued  by sleep. There are, therefore, fewer worldly thought  waves in the atmosphere at night. Flowers bloom in  those late hours. At that time the atmosphere has a  unique, energizing effect. If you meditate then, your mind will easily become one-pointed and be absorbed in meditation for a long time. Night is the time when the yogis remain awake."

—AMMA