That makes no sense. Because if you are in a place where they are 3 hours ahead for example, then you'll miss whatever appointment you had or event you needed to be reminded off. If it notifies you at 10am for something that already happened at 7am where you are.
That is, the time in relation to where you are will be wrong, so you'll either be late to the event or be too early. Either way, its not a good thing.
Either way the time shown in the calendar event will reflect the original time and timezone you set it to it will not change in the event details at all, but may show the time in the timezone it detects you are in.
The relative time it notifies you of the event will be related to the actual time set for the device.
As said, you can turn off the Automatic time changing based on zone in Settings on iOS and iPadOS devices and System Preferences on Mac.