It’s more than just 25, they often go to 29, to indicate 5am. They do this to make it clear that it is an overnight service starting in one calendar day and terminating in another. It’s not just a simple substitute for “1 am”.
Now that I’m a morning person, the same concept of 5am semantic days still works perfectly. The day begins about 20min before my alarm.
I haven't noticed 25:00, but I don't often look at printed/PDF timetables nowadays.
https://developers.google.com/transit/gtfs/reference#stop_ti...
If a coffee shop opens at 5am, they say that. They never say 29.
If a bar stays open UNTIL 5am, they say 29.
Your return flight leaves at 2 and arrives at 11. (2 AM to 11 AM that same day)