Maybe I jumped the gun just a little too quick :-/
To begin, I have the time and regions etc set correctly in my Vera 2 unit as I am using other scenes with the sunrise / sunset option with no problem.
I installed the day / night plugin and created a scene, with the help of the dsc alarm plugin, to turn a light on when the front door was opened and turn it off 30 seconds later.
When tested this all worked great - open the door, light turns on and 30 seconds later it switches off. But it was night.
I tested this morning, 9am, local time so def after sunrise, and the light still turns on when the door is opened.
What could I have done wrong? I was of the understanding that you use the day / night plugin in the usual way you do with all other devices when creating a scene - if you want it t run only at night click the night switch at the beginning of the scene creation and vice versa for day.