Are they different from "nighttime" and "daytime"?
Do night and nighttime require darkness? Do day and daytime require light? Do our clocks help clarify the definition, or is lightness/darkness the definer? Or does the monthly calendar have something to do with it? What about people who live in the extreme northern or southern hemisphere…what is day, and what is night?
The universally used "Daylight Saving Time" is only a matter of changing the clocks, shifting human activity by one hour…earlier or later.
Then the question of "morning" and "evening" complicates things. When does morning begin; and when does nighttime begin? Are morning and evening little more than buffer zones?
Maybe morning begins when we wake up for breakfast, regardless of the time on our clocks. And maybe night begins when we turn off the television, finish our computer emails, and go to bed.
What about the "cocktail hour"? Is that late afternoon, evening, or early nighttime?
It's all too complicated for me!