[lysium]

This will result in incorrect behavior when, between converting to UTC and back to the original timezone, the timezone database has changed, which happens more often than you think.

[GoblinSlayer]

If time is stored in UTC, the result is correct even if the timezone database is corrupted, because timezone is only metadata and doesn't affect time.

[drysart]

Depends what you're actually storing. There are plenty of cases where the timezone is not metadata; it defines how the datetime should be interpreted.

For example: your local mom and pop corner store's daily opening and closing times. Storing those in UTC is not correct because mom and pop don't open and close their store based on UTC time. They open and close it based on the local time zone.