Rio de Janeiro time zone — UTC-03:00 right now (UTC-03:00)

from datetime import datetime
from zoneinfo import ZoneInfo

now = datetime.now(ZoneInfo("America/Sao_Paulo"))
print(now.isoformat())      # local time with offset
print(now.tzname())         # current abbreviation
print(int(now.timestamp())) # unix — same number everywhere

const tz = 'America/Sao_Paulo';
const now = new Date();
console.log(now.toLocaleString('en-GB', { timeZone: tz }));
// ISO 8601 with the zone's offset:
console.log(new Intl.DateTimeFormat('sv-SE', { timeZone: tz,
  dateStyle: 'short', timeStyle: 'medium' }).format(now));

loc, err := time.LoadLocation("America/Sao_Paulo")
if err != nil { log.Fatal(err) }
now := time.Now().In(loc)
fmt.Println(now.Format(time.RFC3339))

import java.time.*;

ZonedDateTime now = ZonedDateTime.now(ZoneId.of("America/Sao_Paulo"));
System.out.println(now);                  // with offset
System.out.println(now.toInstant());      // UTC instant

var tz = TimeZoneInfo.FindSystemTimeZoneById("America/Sao_Paulo");
var now = TimeZoneInfo.ConvertTime(DateTimeOffset.UtcNow, tz);
Console.WriteLine(now.ToString("o"));

// chrono = "0.4", chrono-tz = "0.9"
use chrono::Utc;
use chrono_tz::Tz;

let tz: Tz = "America/Sao_Paulo".parse().unwrap();
let now = Utc::now().with_timezone(&tz);
println!("{}", now.to_rfc3339());

$now = new DateTimeImmutable('now', new DateTimeZone('America/Sao_Paulo'));
echo $now->format(DATE_ATOM), PHP_EOL;

SELECT now() AT TIME ZONE 'America/Sao_Paulo' AS local_time,
       extract(epoch FROM now())::bigint AS unix_seconds;

TZ='America/Sao_Paulo' date +"%Y-%m-%dT%H:%M:%S%z"
TZ='America/Sao_Paulo' date          # human readable