US/Eastern offset

[Chris Angelico]

On Sat, Dec 24, 2016 at 6:51 AM,  <jladasky at itu.edu> wrote:
> On Thursday, December 22, 2016 at 5:57:42 PM UTC-8, Chris Angelico wrote:
>> On Fri, Dec 23, 2016 at 12:54 PM,  <j... at itu.edu> wrote:
>> > Wouldn't most users prefer that modern time zones be the default information returned by pytz, instead of 150 year-old historical time zones?
>>
>> They're the *same* time zones.
>>
>> ChrisA
>
> Apparently, they're not quite the same.  The four-minute discrepancy between New York local (mean solar?) time and the modern time zone is what got Skip Montanaro asking questions.

Is "US/Eastern" the same thing as "America/New_York"? According to my
system, they are symlinks to the same content. So they are actually
the same time zone. It's a time zone that has different UTC offsets at
different points in time, both historic (the change from local to
standard time) and modern (a twice-yearly shift in clocks), but it's
the same timezone. If you look at any other form that means "New_York"
(eg "EST"), and then set the date way back, you should see the same
phenomenon.

ChrisA