DST meetings: a local time can be missing or occur twice
In America/New_York, 2026-03-08 02:30 does not exist: clocks jump from 02:00 to 03:00. On 2026-11-01, 01:30 occurs twice, at UTC 05:30 and UTC 06:30. A date, IANA zone and offset identify which meeting instant you mean.
Worked comparison
A local clock reading is not always a unique instant. On spring transition day, 01:30 at UTC−05:00 is UTC 06:30 and 03:30 at UTC−04:00 is UTC 07:30: only one hour passes. On autumn transition day, the two 01:30 readings are one elapsed hour apart. A fixed label such as UTC−05:00 cannot stand in for New York across the year.
This table scrolls horizontally on small screens.
| New York local time | Offset | UTC instant |
|---|---|---|
| 2026-03-08 01:30 | UTC−05:00 | 2026-03-08 06:30 |
| 2026-03-08 02:30 | No occurrence | No instant |
| 2026-03-08 03:30 | UTC−04:00 | 2026-03-08 07:30 |
| 2026-11-01 01:30 (first) | UTC−04:00 | 2026-11-01 05:30 |
| 2026-11-01 01:30 (second) | UTC−05:00 | 2026-11-01 06:30 |
A mistake to avoid
Scheduling “01:30 New York” without a date or occurrence leaves an ambiguous invitation. Subtracting local clock readings can also misstate duration: 01:30 to 03:30 in the spring example is not two elapsed hours. Work Hours and Time Card do clock arithmetic without a work-location zone and do not inherit this converter’s DST behavior.
Apply it to your calculation
- In the converter, enter the date, local time and IANA source zone. Resolve both results if a time repeats; a missing time is rejected.
- For a 60-minute meeting on 2026-01-15, set UTC as anchor, search one day and enter Asia/Seoul 09:00–18:00 plus Europe/London 07:00–15:00.
- One candidate can be written in an invitation as: 2026-01-15, Asia/Seoul 16:00–17:00 (UTC+09:00); Europe/London 07:00–08:00 (UTC+00:00); 60 minutes, UTC 07:00–08:00. Use the selected candidate’s full date, start/end and offsets, then confirm availability in actual calendars.
Sources and limits
The planner checks candidate starts every 15 minutes and excludes local Saturdays and Sundays. It does not read calendars or national holidays and cannot guarantee attendance. Conversion uses browser/system Intl data; its exact tzdb version is not exposed. Time-zone rules may change, so review future meetings after software updates.
Example notes updated: