%z is -0400 This format is not standard. if your machine is configure as Eastern Date Time
%Z is EDT if your machine is configure as Eastern Date Time, not too much use for storing it in data base. By the way I live in New York.
%:z is -04:00 That is the one most useful in hours and minutes. It can be used across computer languages
%::z is -04:00:00 It is over kill. we don't need second for time zone
%:::z is even more over kill, no use in reality
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