"Friday 08:00 at my location" is not necessarily the same as "Friday 08:00 London time" is not necessarily the same as "Friday 08:00 UTC+1", but it's very difficult to ask the user which of these they mean in a way they'll understand.
I (very occasionally) work on some software that schedules web content to appear at a certain future time. We had a bug once where during summer, an editor had scheduled an item to appear a few weeks in the future, at 09:00. We displayed this time back to them in our current local timezone (but presumably stored it as UTC), and it looked correct. When that scheduled date came, our timezone had reverted to winter time, and the content appeared an hour late.
We should have displayed the scheduled time in "what the local timezone would be at the scheduled time", or stored the time with a timezone expressed as a location rather than a UTC offset.
I (very occasionally) work on some software that schedules web content to appear at a certain future time. We had a bug once where during summer, an editor had scheduled an item to appear a few weeks in the future, at 09:00. We displayed this time back to them in our current local timezone (but presumably stored it as UTC), and it looked correct. When that scheduled date came, our timezone had reverted to winter time, and the content appeared an hour late.
We should have displayed the scheduled time in "what the local timezone would be at the scheduled time", or stored the time with a timezone expressed as a location rather than a UTC offset.