Giorgio, I set my system region / locale and language settings to Italiano, system timezone to UTC + 1 Roma, my SmarterMail web language to Italiano, and SmarterMail user timezone to UTC + 1. Unfortunately, I am not seeing the issue you've reported. What are you server settings? Your browser settings? You may find it helpful to open a support ticket. This way we can see your system configuration and have access to your calendar data. If it's a bug, your ticket will be refunded.