Aren't timezones an offset of UTC by definition? I thought during daylight savings time a country is temporarily changing their timezone. Isn't that why we have EST and EDT: they're two different timezones?
No, time zones are a specific geo region that follows a certain time standard. The standard has a relative reference to UTC but that reference may change, either regularly or randomly.
Eastern Time Zone is a single time zone, that has different offsets depending on season, formally referred to as EDT and EST to make it easier to identify as daylight or standard references to UTC.
Even regions within the same time zone don't follow the standard exactly, so Panama does not observe daylight saving time while New York does. This is why we have even more granular settings used for calendars and dates.
Eastern Time Zone is a single time zone, that has different offsets depending on season, formally referred to as EDT and EST to make it easier to identify as daylight or standard references to UTC.
Even regions within the same time zone don't follow the standard exactly, so Panama does not observe daylight saving time while New York does. This is why we have even more granular settings used for calendars and dates.