夕方 and 夜: early evening and night
Talk about the end of daylight and nighttime, checking the range marked by particles.
Toward evening
夕方 (ゆうがた) refers to late afternoon or early evening as daylight ends. 「夕方に買い物に行きます」 says the speaker will go shopping then.
「夕方になると涼しくなります」 says it gets cooler toward evening. Do not add an exact hour absent from the sentence.
Nighttime plans
夜 (よる) means night. 「夜は家で勉強します」 describes studying at home at night.
「今夜、電話します」 promises a call tonight. 今夜 is read こんや, distinct from よる for 夜 alone.
A boundary that can overlap
The boundary between 夕方 and 夜 depends on context. An expression such as 「夕方六時」 is clearer than naming only a time of day.
「夕方から夜まで歩きました」 means walking from early evening into the night. まで marks the endpoint of that walking period.
Does 夕方 always mean six in the evening?
Show the answer and why
No. It is a broad time-of-day expression. Confirm an exact hour for a precise appointment.