assalamu alaykum,
Each day contains 24 hours, some of those hours are going to be in darkness (night) and other hours will be with light (daylight). So from Islamic perspective, the Quran and Sunnah show that the night begins before the day. As the sun sets, the night for the next "day" has begun and then when the sun rises the daytime for the day begins. I hope this is not confusing.
From modern, Western sense the next day effectively begins at 12 Midnight. We just think of it as a few hours before, so it is not really a big issue. Perhaps this is what confuses people.
This is also the same as how Judaism and Christianity thought of a day too according to the Bible and Torah, that it begins after sunset.
This is how when Ramadan begins we pray taraweeh in the night before the first day of fasting. Effectively our first night of ramadan begins before the first day of fasting, although it is the same "day". Similarly the Eid night is due to the moon sighting and when the daylight comes we pray the Eid in the morning and celebrate during the day. When Maghrib time comes that day has effectively finished.
. because after magrib it is considered next day HOW?
