Night's not really ambiguous - it's anytime when the sun is down. I find it tough to know in other languages when to use "night" and when to use "evening".
"Evening's" basically absent from my dialect except in the distinction between "good evening" (a greeting) and "good night" (a farewell).
Let's see whether I can distinguish "evening" vs. "night." The former starts when the afternoon sky noticeably becomes darker (Though the sun is still visible!) and continues after sunset right to the point that most normal people with a day job either get sleepy, or feel that they ought to be in bed. All the dark time afterward becomes "night," which belongs to sleeping or getting ready for it. This definition certainly applies to the latitudes for Middle America, but I can't say the same for St. Petersburg, Montmartre, or Madrid, where nobody thinks of dinner before 22:00, ¡jamás!