Translation:Saturday is the last day of the Klingon week.
The Klingon week is six days long, and the last day is ghInjaj. You start adding jaj wa', jaj cha' and so on for foreign calendars.
This sentence is not only correct, it goes out of its way to specify what kind of week it's talking about.
It seems clear to me that this is Okrand's way of making a joke about whether Sunday is the first day of the week or the last, an argument we have all the time here on Earth. In Klingon, it's both: it's called jaj wa' day one, and it's the last day.
Ah, I interpret it as Klingons starting off naming alien weekdays after Klingon ones and if there are more than six in a given culture, then any extra, last, ones being numbered as jaj wa', jaj cha', etcetera. I remember at the time seeing it as a clever resolution to his naming Sunday jaj wa' in a Vegas invitation, before thinking about the fact that a lot of the world, and logic, put Sunday last.
I don't have the precise reference, but AK is usually trustworthy: http://klingonska.org/ref/time.html
I can see how you might argue that this doesn't necessarily make jaj wa' last, but it's much stronger that its being definitively first.
I interpret it as Klingons starting off naming alien weekdays after Klingon ones and if there are more than six in a given culture, then any extra, last, ones being numbered as jaj wa', jaj cha', etcetera.
That's how I interpret it too, because that's how it was reported. I'm saying that jaj wa' is literally translated as day one, and it's the last day when described in Klingon.
As for logic, it's perfectly logical for the "weekend" to mean a Sunday at the week's front end and a Saturday at its back end. It's also perfectly logical to put Sunday at the end for a single block of "weekend." Which one is done is just a matter of convention; neither is more logical than the other.