In airline travel, how does Saturday-night stay pricing work for multi-city itineraries?

For a roundtrip booking it is pretty clear what the destination is, but less so for more complicated itineraries. I've been playing with some transatlantic trips in online booking tools and I'm not getting a clear intuitive sense for how this works (i.e. where I need to spend the Sat night to get good pricing).

I mainly fly OneWorld carriers but would be curious to learn how this works for other airlines too.

edit: In the comments there appears to be some doubt about whether Sat night stay is still a thing, but I see this sort of price graph all the time (maybe it's an international/transatlantic/OneWorld thing?):

price graph

Here is a direct copy-and-paste from britishairways.com for a booking I'm looking at right now:

britishairways.com screenshot

"first sun after arrival at turnaround" — how do they define "turnaround" if it's a multi-city trip?

marked as duplicate by Giorgio, Aganju, user79658, Ali Awan, gmauch Nov 18 '18 at 16:50

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  • What is this question about? What's so special about Saturday night stay? – Neusser Nov 16 '18 at 13:38
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    Keep in mind, the "Saturday night stay" is not as big a thing as it used to be. I don't recall and recent incident (in the dozens of times I've flown) where it made a difference. – Johns-305 Nov 16 '18 at 15:19
  • @Johns-305: I see it all the time — and very clearly — looking at price graphs of BA and other OneWorld carriers. It definitely continues to exist as a phenomenon, albeit one that's a little bit hard to pin down. Doubly so for multi-city itineraries, hence the question. :) – NPE Nov 17 '18 at 1:38
  • @NPE That's why I said specifically "not as big...as it used to be". I did not say it wasn't a thing. I remember when every itinerary priced differently with a SnS. Now, not so much, especially for independent carriers like Norwegian which seem to price every segment independently regardless of itinerary or length of stay. – Johns-305 Nov 17 '18 at 15:10