When creating a new Calendar or modifying an existing one via UVC and adding the Special Days for the Netherlands King's Day ( displayed as Queen's Birthday) will be added the 30th April instead of the 27th April.
The 30th April used to be the previous Holiday ( Queen's Day) .
It was switched in 2014 to the 27th April ( King's Day).
Update to a fix version listed below or a newer version if available.
Version: 6.9.21 - Released 3th July 2018