Inherit time format (12-hours / AM/PM vs 24-hours) from GNOME Settings when available
There is an operating-system-wide portalled setting for this, since at least 2019. Evolution should inherit it, and/or connect its UI radio buttons to it, so that it is consistent with the rest of the system.
I don't think it makes sense to have per-app divergence, but if you still want to have the ability to override, I guess you could do something similar to what was done for the timezones setting.
Edited by Jeff Fortin