RaidPlanner is timezone aware. It means if you setup an event for 21:00 it means 21:00 on your time, every users with different timezone setting should see the event time adjusted for their own timezone.
Please check, that your (user) timezone and server timezone has correctly configured. If so, and it still not working, please let me know your joomla version, server timezone setting, and your timezone setting.
Thx.
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