I've been working on a book about Idioms & Phrasal verbs.
As I was working, I came across the following definition for the phrase a night out: An evening you spend out of the house enjoying yourself (also a day out)
I made some research from which I got the following definition of a day out: A day where you go out somewhere for fun or enjoyment - macmillan dictionary
From the same dictionary, day is defined as one of the periods of time that a week is divided is divided into, equal to 24 hours. Now from cambridge dictionary, we get new datum: A period of 24 hours, especially from twelve o'clock one night to twelve o'clock next night.
I've read some examples from the following dictionaries too: https://www.ldoceonline.com/dictionary/day-out and https://www.oxfordlearnersdictionaries.com/us/definition/english/day-out
They do not specify whether it's all day long or a specific period of the day. Thus the definition given in the book I'm reading is wrong, isn't?