My stop time is the 16:00 London fix rather than a UTC hour. On a month end Friday especially, the half hour before the fix carries the real flow, and after it the EURUSD book visibly thins.
The partial reversal held in my notes only when the week had already travelled a long way. If a pair was up more than about 1.5 times its average weekly range by Friday lunchtime, some giveback was common, while ordinary weeks just drifted.
Pending orders are the one thing I clean up without exception. A buy limit left 10 pips under price can fill on a thin wick and then sit open over the weekend.
Prop accounts make it stricter. One firm I used counted its cut off on server time, two hours ahead of London, so 23:59 on the server was really 21:59 London and not midnight.
The clock change gap is worth knowing about too, since Europe moves back a week before the US does this year. For that one week the New York close lands at 21:00 London instead of 22:00, and the thin hours start earlier.
Do you treat month end Fridays differently from the rest? I tend to stop even earlier on those.
