What is 'night time'?

[LagoDiComo]

We have a lively cat, he's about 2 (rescue so not 100% sure). He is very nocturnal and only really wants to go out when it's dark. We tend to get him in at night by 11pm at the latest and he will sleep for a few hours.

He then wakes us up every morning at 5am wanting to go out. It's obviously still dark at 5am. We are getting a cat flap fitted and we will set the opening and closing times. We aren't sure about the AM opening time, since his natural tendency is to want to get out at 5am (and it would be good if he could go without waking us up) but is this too early? (Obviously timings change a bit through the seasons). What time is the end of the night?

Also if you have a cat flap with opening /closing times, how does your cat deal with this?

Mine has free access to the cat flap 24 hours, but I do live in a quiet, rural location.

I should probably add that we live in central London! When I was growing up my parents let our cats out all night but I understand it is ideally better to keep them in at night.

Is he just popping out for the loo, or does he use a litter tray and just like to roam? I would have thought in an urban area 5am would be safer than the middle of rush hour? I used to live in SE London and cat at that time had 24 hour access as well, but it was a quiet area again, with lots of commons and woods.

It may be the call of nature as if we stop him going out (until it's lighter) he immediately uses his tray. If it's that it hopefully he'll come straight back in afterwards. He is currently locked in all day when we are at work so are also hoping if he can come and go during the day, he'll have less energy at night