I'm using midday in this context...
https://forum.keyboardmaestro.com/t/km-dates-times-notes-on-anchors-intervals-and-translations/1935/4
" Keep in mind that TIME is in GMT and the output of ICUDateTimeFor is in local time, so when doing this sort of thing it is best to use midday instead of midnight:
%ICUDateTimeFor% TIME(2015, 8, 23,12,0,0) %EEE, MMM d, yyyy%
which will generally work anywhere since at midday GMT, the entire world (almost) is on the same date. Otherwise, folks with negative GMT offsets (which includes all of the Americas for example) will get the wrong result."
...and as you point out I was confusing absolute and dynamic "gmt offset"
Dave