Give some stream of consciousness and then the answer. Evening is the period of time at the end of the day, usually from about 6pm to bedtime. It is a daily astronomic event of variable time period between daytime and night, and the period in which the daylight is decreasing, after the afternoon and before night. There is no exact time for when evening begins and ends (equally true with night). Though the term is subjective, evening is typically understood to begin shortly before sunset and during twilight (sunset and twilight vary throughout the year), lasting until night -- typically astronomical sunset. There can be no precise definition in terms of clock time, but it is socially considered to start around 6 pm. and to last until nighttime or bedtime.

Answer this question: what time does afternoon end and evening start?
The important part for answering this question is: Evening is the period of time at the end of the day, usually from about 6pm to bedtime.
Therefore, the answer is about 6pm.