for tz in America/New_York Europe/Madrid; do
   export TZ="$tz"
   printf 'TZ=%s\n' "$TZ"

   printf 'Expect: '
   printf '2021-08-04T22:55:12+0000\n' |
      perl -M5.010 -MTime::Piece -nle'
         my $epoch = Time::Piece->strptime($_, "%Y-%m-%dT%H:%M:%S%z")->epoch;
         say $epoch;
         say localtime($epoch)->strftime("%Y-%m-%dT%H:%M:%S%z");
      '

   printf 'Got: '
   printf '2021-08-04T22:55:12+0000\n' |
      jq -Rr 'gsub("[+]0000"; "Z") | fromdateiso8601'
   printf '2021-08-04T22:55:12+0000\n' |
      jq -Rr 'gsub("[+]0000"; "Z") | fromdateiso8601 | localtime | strftime("%Y-%m-%dT%H:%M:%S%z")'

   printf '\n'
done


TZ=America/New_York
Expect: 1628117712
2021-08-04T18:55:12-0400
Got: 1628121312
2021-08-04T19:55:12+0000

TZ=Europe/Madrid
Expect: 1628117712
2021-08-05T00:55:12+0200
Got: 1628121312
2021-08-05T01:55:12+0000