9am in Sydney is 8am in Seoul

Sydney is 1 hour ahead of Seoul. Seoul runs on Asia/Seoul (UTC+9); Sydney runs on Australia/Sydney (UTC+10). The difference is measured right now; it can shift by one hour during daylight-saving-time transitions.

Sydney observes daylight saving time — shifting between AEST (UTC+10) and AEDT (UTC+11) — while Seoul stays on KST (UTC+9) year-round. The difference is 1 hour in Sydney’s winter and 2 hours in Sydney’s summer. Transitions happen in late March and late October for most Northern-Hemisphere DST zones, and late September/early April for Southern-Hemisphere ones — check the current date against the city’s DST schedule before anchoring a meeting at the edge of those windows.

Standard 9-to-5 business hours in Seoul and Sydney overlap for roughly 7 hours a day. That window lands at 09:00–16:00 in Seoul and 10:00–17:00 in Sydney. Teams with real-time coordination needs anchor cross-city calls inside it: long enough to cover handovers, short enough that it forces crisp agendas. Outside that window, async is the default — shared docs, recorded updates, and scheduled follow-ups rather than live meetings.

When planning recurring meetings across Seoul and Sydney, pin them to one city’s local time rather than UTC or the other city’s clock. That way, the meeting time stays stable for the person anchoring the schedule, and the other side absorbs the one-hour drift during DST transitions. The alternative — a meeting pinned to the non-DST city — means the DST city sees the meeting time “move” twice a year, which is how recurring calendar invites end up at 7am on someone’s calendar in October.