I ran into this problem when I started teaching composition to Chinese students: they kept using evening as if it were afternoon, and I kept telling them they were wrong. The next semester I looked it up and this is what I found for "evening" in Merriam-Webster 3rd international:
- a) the latter part and close of the day and early part of darkness or night
- b) chiefly South & Midland : the time extending roughly from noon to twilight : afternoon; "It was about 3 o'clock in the evening."
- c) the part of the day from noon to midnight — used in the Bible
- d) the period from sunset or from the evening meal to bedtime
So they were sort of right; though I still reject noon to midnight since we aren't living in Biblical times, and also the argot of the "south and midland" (where is that?), which has evening but no afternoon.
But no matter how you cut it, evening means the early part of the night; this is why we say good evening as a greeting. Night is not just night, it is later than evening, hence good night is a farewell.
After looking up lots of stuff, I also thoroughly convinced myself that twilight is definitely a part of evening for many many people, even though I had rejected the idea before. Try checking out song lyrics. Result: big loss of face (I had to tell them). Teachers, be cautious of overconfidence!