The best time of day to paint varies depending on the indoor space you're painting. You want to paint at whatever time the room gets the most natural sunlight. Natural sunlight makes it easier to see bare patches as you paint and as you apply touch-up paint.
Check the upcoming forecast and try to paint on a hot day. Indoor latex paints work best at temperatures above 50 degrees Fahrenheit. On a hot day, you'll also be able to open windows for paint fume ventilation.
While hot days are good, make sure you paint during a dry heat. In humid conditions, paint dries much slower.