Opposite seasonal shifts
London and Sydney move their clocks in opposite seasons, making a single year-round difference unreliable. A London early start can meet Sydney late in the day. Check both seasonal examples and decide explicitly whether the London or Sydney wall-clock time should anchor a recurring series.
London, GB: Europe/London (city ID: london).
Sydney, AU: Australia/Sydney (city ID: sydney).
Does the difference change?
The destination-minus-source differences sampled on the 15th of each month in 2027 are +9h, +10h, +11h. These are dated examples, not a promise of fixed offsets or a complete historical range. A different reference date may have different rules.
| Source date | London | Sydney |
|---|---|---|
| 2027-01-16 | 10:00 Greenwich Mean Time | 2027-01-16 · 21:00 Same day · Australian Eastern Daylight Time |
| 2027-07-16 | 10:00 British Summer Time | 2027-07-16 · 19:00 Same day · Australian Eastern Standard Time |
Daylight-saving rules depend on the city and date. When a local hour is missing or repeated, the converter rejects it or asks which occurrence you mean. Rules can change politically; reconfirm far-future meetings.