AEST to EST: time zone conversion

AEST is UTC+10 and EST is UTC−5, so on paper you subtract 15 hours. In practice Sydney and New York are never both on standard time. Sydney keeps AEST from April to October, while New York is on EDT, and AEDT, UTC+11, from October to April, which covers New York’s EST months. So the real gap between the two cities runs from 14 to 16 hours.

Through 2026

Jan 1  – Mar 8    AEDT → EST    UTC+11 → UTC−5    16 hours
Mar 8  – Apr 5    AEDT → EDT    UTC+11 → UTC−4    15 hours
Apr 5  – Oct 4    AEST → EDT    UTC+10 → UTC−4    14 hours
Oct 4  – Nov 1    AEDT → EDT    UTC+11 → UTC−4    15 hours
Nov 1  – Dec 31   AEDT → EST    UTC+11 → UTC−5    16 hours

Sydney’s clocks change on the first Sunday of April and of October, both times at 16:00 UTC on the Saturday: on April 5 they go back from 03:00 to 02:00, and on October 4 they jump from 02:00 to 03:00. Melbourne, Canberra and Hobart follow the same rules. Brisbane doesn’t: Queensland keeps AEST all year, so Brisbane is 15 hours ahead of EST and 14 ahead of EDT.

A worked conversion

The tool below starts at 09:00 in Sydney on Wednesday, July 15, 2026, when Sydney is on AEST:

2026-07-15 09:00 Australia/Sydney (UTC+10:00, AEST)
2026-07-14 19:00 America/New_York (UTC-04:00, EDT)

In January the same 09:00 in Sydney is AEDT, and New York reads 17:00 EST the day before.

Meeting window

Sydney’s morning meets New York’s afternoon or evening of the previous day: 08:00 AEDT in January is 16:00 EST, and 09:00 AEST in July is 19:00 EDT. Friday afternoon in New York is already Saturday morning in Sydney, and Monday morning in Sydney is still Sunday in New York, so a weekly slot has to avoid both ends of the week.

Abbreviation traps

AEST is Sydney’s winter name; from October to April it’s AEDT. Before 2014 the tz database itself called Australian Eastern time EST, so older logs and systems can say EST and mean Sydney. As a zone name, AEST is rejected: Node.js 22 throws RangeError: Invalid time zone specified: AEST, Python’s ZoneInfo("AEST") raises, and GNU date with TZ=AEST prints UTC under an AEST label. Use Australia/Sydney (or Australia/Melbourne, Australia/Brisbane) and America/New_York; the tool below reads AEST and AEDT as Australia/Sydney and notes when Sydney is on the other one. With en-US, Intl labels Sydney GMT+10; en-AU gives AEST or AEDT.

In code

from datetime import datetime
from zoneinfo import ZoneInfo

datetime(2026, 1, 15, 9, 0, tzinfo=ZoneInfo("Australia/Sydney")).astimezone(ZoneInfo("America/New_York")).isoformat()
# '2026-01-14T17:00:00-05:00'

TZ=America/New_York date -d 'TZ="Australia/Sydney" 2026-07-15 09:00'    # GNU date
# Tue Jul 14 19:00:00 EDT 2026

new Date('2026-07-14T23:00:00Z').toLocaleString('en-US', { timeZone: 'America/New_York', timeZoneName: 'short' })
// '7/14/2026, 7:00:00 PM EDT'