1. The origin of "at night" to indicate a point of time and the usage of prepositions "in" and"at" In olden times, when the time expression "at night" was originated, night might have been thought as a point of time in the day because there wasn't any activity going on and people were sleeping that time unlike daytime. At Night or In the Night?

Understanding the Context

- English Language & Usage Stack Exchange The spoken use of "night" as an informal, familiar version of "good night" (wishing one a restful sleep) is common, but I'm not sure what the proper written equivalent is - if there is one. The expression by night is typically used to contrast someone's nighttime activities to their daytime activities, especially when the nighttime activities are unusual or unexpected. 4 Day and night time is not an idiomatic or set phrase (unlike day and night), but it can be used appropriately in certain contexts, particularly in technical ones. Here is a relevant usage I've found: The English word day can be used to refer to the time of daylight or to the unit of time that encompasses both day and night time.

Key Insights

Can we use "day and night time" instead of "day and night"? In this night of wonder or On this night of wonder, which is correct? The full context is God from heav’nly splendour Comes to earth below; In/On this night of wonder, The world is all aglow. On this night vs In this night - English Language & Usage Stack Exchange