When Does Night Officially Begin? Confusion Over Time and Darkness

I mean when we start saying it's night time.
I have always been convinced that the night is completely dark.
So, for example, now it is 6:55 pm it is completely dark, so for me it is night
I was surprised that there is a day for some of my friends.
So I asked when is it going to be night?
Night will be after 22
They couldn't explain to me why 22.
My guess is that it was about summer time when it gets completely dark at 22:00.
They answered me yes
So why exactly did they take daylight saving time as their reference point and not now?
And again no answer ...........
I am very interested in the opinion of you forum members as it is with this night.

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After 10 pm - it is most often said about curfew

For some, all night is daytime - especially Saturday nights - and then during the day they sleep at night ...

I had the same dilemma when writing Astronomical Clock software. When and how to define dawn?
There are many definitions! For example, when the disc of the solar disk touches the horizon or "hits the horizon" to a certain extent.
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And by the way, I have always lived in the belief that the night silence starts at 11 p.m. and ends at 6 a.m. (which does not apply to emergency services - ambulance drivers can make noise even at 1 am). Never mind.
Regards