One of the oldest #GNOMECalendar core feature requests might become possible in #GNOME 48: basic timezones editing for events (brought to you by @titouan_real)!
If you would like to help, grab the flatpak artifacts (or build yourself using GNOME Builder) from this branch/MR, and test it thoroughly, so that it can hopefully land bug-free into nightly: https://gitlab.gnome.org/GNOME/gnome-calendar/-/merge_requests/516
As this is experimental for now, we recommend you back up your data and test using only spare/throwaway calendars.