ANS:
The standard varies by culture. For example, the Indonesians divide the day into 4 distinct parts:
Pagi “morning” is from midnight until about 11 am.
Siang “noon” is from about 11 am to 3 pm.
Sore “afternoon” is from 3 pm to 6 pm.
Malam “Evening” is from 6 pm to midnight.
These distinctions are in everyday use. “Selamat pagi” means good morning. “Selamat malam” means good evening. Indonesians also say “selamat siang” and “selamat sore”, “good noon” and “good afternoon”. Selamat hari means “good day”.
Dinner is referred to as “makan malam”, literally “evening eat”. “Makan siang” is lunch, and makan pagi is breakfast, though “sarapan” is more commonly used for the morning meal.
The sun is called “Matahari” in the Indonesian language, “mata” = eye and “hari” = day, so the sun is literally the “Eye of the Day”. It’s beautiful, logical language.