Seems that when we create a segment using the "Server time - hour" dimension, it does match visits using the UTC visit time (hour).
For example creating a segment matching visits from "server time - hour" = 6, it shows visits from 8PM (the website is configured in UTC+2).
Also reported by a customer
UTC timeinstead of
Server time. but this could be confusing as timezones conversions are hard for everyone)