Australia–UK Meeting Times — Opposite-Hemisphere DST
London and Sydney are 9 hours apart when London is on daylight time and Sydney on standard time, and 11 hours apart in UK winter / Sydney summer, because the two hemispheres change clocks at opposite times of year. The only honest overlap is UK morning ↔ Sydney evening. Anchor to London; Sydney floats.
Sydney and London sit 9, 10, or 11 hours apart depending on the season, because the two hemispheres add daylight saving in opposite halves of the year — the widest swing of any common corridor. In the 12 months from September 2026 the gap runs 9h, peaks at 11h during UK winter / Sydney summer (weeks of 26 Oct 2026 → 29 Mar 2027), and settles back to 9h from the week of 5 April 2027. Hold the series on London time, let Sydney float, and expect the Sydney hour to swing two hours across the year.
Sydney and London sit 9, 10, or 11 hours apart because the hemispheres change clocks in opposite seasons, so both sides move. The gap peaks at 11h in UK winter / Sydney summer. Anchor to London; the honest overlap is UK morning ↔ Sydney evening.
Direct Answer
Sydney and London sit 9, 10, or 11 hours apart depending on the season, because the two hemispheres add daylight saving in opposite halves of the year — the widest swing of any common corridor. In the 12 months from September 2026 the gap runs 9h, peaks at 11h during UK winter / Sydney summer (weeks of 26 Oct 2026 → 29 Mar 2027), and settles back to 9h from the week of 5 April 2027. Hold the series on London time, let Sydney float, and expect the Sydney hour to swing two hours across the year.
Why This Matters
Most DST problems are one-sided: one country changes, the other stays put, and the gap moves by a single hour. Australia and the UK are the worst case, because both sides change — in opposite seasons. When the UK is on standard time (GMT), Sydney is on daylight time (AEDT); when the UK is on daylight time (BST), Sydney is on standard time (AEST).
The two clocks always move in opposite directions, so their offsets diverge and converge by the full two hours: 9h at the most convenient point, 11h at the worst. The gap does not just widen — the shape of the day inverts. In the 9h regime, a 09:00 London meeting is a tolerable 18:00 in Sydney. In the 11h regime, the same 09:00 London meeting is 20:00 in Sydney — a late-evening start that many teams cannot sustain.
The Drift Calendar: Four Changes in 12 Months
These are the exact drift weeks for the next 12 months (computed from the current timezone database on 27 August 2026, for a weekly series starting the week of Monday 7 September 2026):
| Month | Which city changes | What happens |
|---|---|---|
| Oct 2026 | Sydney | Mon 5 Oct: AEST (UTC+10) → AEDT (UTC+11), clocks forward |
| Oct 2026 | London | Mon 26 Oct: BST (UTC+1) → GMT (UTC+0), clocks back |
| Mar 2027 | London | Mon 29 Mar: GMT (UTC+0) → BST (UTC+1), clocks forward |
| Apr 2027 | Sydney | Mon 5 Apr: AEDT (UTC+11) → AEST (UTC+10), clocks back |
Four changes in twelve months — two per side — is the maximum any corridor can produce, and it is exactly what this one does.
Decision Table: The Gap by Season
Sydney is always ahead of London. The gap depends on which regime each side is in:
| Regime (window) | Gap | Sydney time at 09:00 London | London time at 18:00 Sydney |
|---|---|---|---|
| 9h — Sydney AEST + London BST (before week of 5 Oct 2026; from week of 5 Apr 2027) | 9h | 18:00 | 09:00 |
| 10h — transition weeks (weeks of 5–26 Oct 2026; 29 Mar–5 Apr 2027) | 10h | 19:00 | 08:00 |
| 11h — Sydney AEDT + London GMT (weeks of 26 Oct 2026 → 29 Mar 2027) | 11h | 20:00 | 07:00 |
Two things to notice. First, the only window where both sides can keep a reasonable hour is the 9h regime: London 09:00 ↔ Sydney 18:00. Second, in the 11h worst case, an 18:00 Sydney meeting is 07:00 in London — effectively unreachable for a London team.
Workflow: Scheduling a Sydney–London Series Across the Inversion
- Anchor the series to London time. London is the more stable side: it keeps the slot inside core working hours 94% of weeks, versus 50% for Sydney, so the London hour of the meeting is the one to keep fixed.
- Expect the Sydney hour to swing two hours across the year. A 09:00 London meeting lands at 18:00 Sydney in the 9h regime, 19:00 in the transition weeks, and 20:00 in the 11h worst case.
- Book the UK morning as the natural slot. The corridor is an evening-for-Sydney corridor year-round; the question is only how late the Sydney end gets. If the team cannot take a 20:00 Sydney start, the 11h window (weeks of 26 Oct 2026 → 29 Mar 2027) is where to suspend or shorten the series.
- Flag the four change weeks — week of 5 Oct 2026, week of 26 Oct 2026, week of 29 Mar 2027, week of 5 Apr 2027 — and re-confirm the Sydney hour around each.
- Use the planner’s drift row to see the affected occurrences before they land, then export the calendar file with each occurrence at its correct local time.
Where TimeNowHub Does the Work
- The London ↔ Sydney comparison shows the live overlap and the seasonal gap for this corridor.
- /time/sydney and /time/london show current local time and whether each city is on a working day right now.
- Open the meeting planner with Sydney and London preloaded to score a recurring slot across both sides’ work weeks and see every occurrence that lands on a changed offset.
Frequently Asked Questions
Why is the London–Sydney gap 9 hours in some months and 11 in others?
Because the hemispheres run daylight saving in opposite seasons. Sydney adds an hour during the northern winter (AEDT), London adds an hour during the northern summer (BST). Their offsets therefore converge to a 9h gap for part of the year and diverge to an 11h gap in UK winter / Sydney summer.
When is the worst-case period?
UK winter / Sydney summer: from the week of Monday 26 October 2026 (London back to GMT, Sydney already on AEDT) to the week of Monday 29 March 2027 (London forward to BST). For those weeks the gap is 11 hours and a 09:00 London meeting is 20:00 in Sydney.
What time of day actually works for both sides?
UK morning ↔ Sydney evening. In the 9h regime, 09:00 London is 18:00 Sydney. In the 10h and 11h regimes the Sydney end slides to 19:00 and 20:00, which is late for a regular meeting — treat the UK-winter stretch as the hard part of the year.
When are the four clock changes in the next 12 months?
Sydney moves during the weeks of Monday 5 October 2026 and Monday 5 April 2027; London moves during the weeks of Monday 26 October 2026 and Monday 29 March 2027. Between the two London changes and the two Sydney changes, a recurring invite shifts four times a year.