[interestednovice]

The Friday difference is because World News America airs as normal for a weekday in the US, whereas London 'covers' that timeslot on weekends. In one sense, 2300 UK time Friday is where the 'weekend arrangements' start and 2300 UK Sunday is where they end

That makes sense - I was aware that 23:00 U.K. time on Sunday was where the weekend arrangements ended, as that is “morning” in Singapore for Newsday. On Friday nights, of course, the reverse occurs - where it’s already Saturday morning in Singapore, and thus no Newsday, but Friday afternoon in Washington and WN America has to air, as you say.

I was being stupid, sorry again!