Start with a named zone and a local date
A city maps to an IANA identifier. The bundled transition data supplies the UTC offset that applies at each instant in the supported range. The selected local date and clock time are resolved against those rules, rather than converted with a single offset remembered for the city.
A local time has zero, one, or two matches
An ordinary wall time resolves to one instant. A forward clock change can leave a gap, giving no matching instant. A backward change can repeat an interval, giving two candidates. The tool requires a correction or explicit skip for a missing time and an earlier-or-later choice for a repeated one. It does not silently equate a shifted time with the input.
Compare intervals on one common axis
Each result row is formatted from the same resolved instant. Working-hour intervals are separately resolved for each participant’s local calendar, converted to UTC, and intersected. The selected meeting must fit completely inside the common interval. A boundary that only touches another boundary has zero duration.
Keep overnight availability attached to its start day
A Monday 22:00–06:00 window begins on Monday and ends on Tuesday. Its Tuesday tail remains available because the interval belongs to the Monday start. The seven-day scan includes intervals that began before the visible boundary when they still overlap the requested range.
Resolve a weekly anchor for every occurrence
A weekly instruction names one anchor city’s local weekday and time. Each of the next twelve dates is resolved independently, so another city may move by an hour or cross a date boundary. The export contains the resolved occurrences as individual events. It does not infer an open-ended recurrence rule from a fixed UTC interval.
Keep display separate from protocol data
The locale controls interface text, number and date formatting, reading direction, and export labels. The 12-hour or 24-hour preference changes presentation. Saved schema fields, IANA identifiers, ISO dates, duration minutes, and UTC timestamps retain their machine meaning. Changing a label does not change an event.
Know what the result does not measure
The planner does not obtain participants’ calendars, public holidays, travel plans, or personal preferences. It does not synchronize the device clock or guarantee a future government rule. Working hours are user-entered assumptions. Use the result to discuss an arrangement and check critical events in the calendar where they will be used.
Data version and review
This build uses IANA 2026f and supports planning years 2026–2035. Static examples are explicitly dated. The data-sources page identifies the rule source, export standard, and attribution files. A data update requires renewed time fixtures, recurrence checks, and export validation before the new build is treated as verified.