Is there now daylight savings in Layout? I have some viewports for diagrams of sun/shadow where I control shadows inside Layout to reduce the number of scenes imported. When I change the date (a model geolocated in Norway, and we have daylight saving from late march until late October) then the time of day also changes. So when I have a viewport set to 21.march (in Layout, overriding the scene), and change that to a corresponding date in April, one hour is automatically added to the time of day.
if I correct the time of day to the same as In sketchup, (with the same manual override to correct for daylight savings) then I get the same shadows in both Sketchup and Layout, so clearly there is no daylight savings in the shadow calculations). So its just that the time of day changes one hour when I cross the daylight savings start date when changing the date. The same does not happen when I change dates within the daylight savings period.