There is no scientific evidence to suggest that spirits prefer to come out at night vs. the day. Many people have reported seeing and hearing ghosts in daytime hours. Some spirits may even prefer the daytime to the night. There is also no real way to know if spirits even know the difference between night and day, as this concept may not even exist in their world.
But is it easier to see a ghost at night? Even though they may appear just as often throughout the day? If ghosts manifest as a result of gathering energy as many believe, then it may indeed be easier to see them at night, when it’s darkest and easier to see any light emitting from the energy. This would also be the case for those spirits that only appear as light.
But you can create a similar nighttime effect with the shades down and curtains closed during the day. Basements and attics, where spirits are often reported to frequent, are usually dark during the day with no lights on.