Time zone research

How We Verify a Time Zone Conversion

This repository verifies its 2026 time-zone examples by deriving offsets from the runtime time-zone database instead of keeping a hand-written offset table. The evidence file covers a selected ten-zone set and a defined weekly-meeting model, so the method and its scope can be checked separately from any broader claim about world time-zone behavior.

By BeanNest Studio Reviewed September 20, 2026

What this guide helps you decide

A time-zone tool reports a conversion. How can that value be independently checked rather than trusted?

This research documents the verification method used for this repository's time-zone evidence. It does not evaluate any third-party tool and does not claim the method covers every edge case.

Try it on the anchor product: BeanNest Time /, BeanNest Time /meeting-planner/, BeanNest Time /converter/.

Sample the configured zones from the runtime database

The generator formats known instants in each configured zone and compares them with UTC to derive the offset in minutes. For the 2026 evidence file it samples ten selected zones hourly across the year. No hard-coded offset table supplies the recorded January, July, or transition values.

Detect a transition when consecutive samples differ

For each configured zone, the generator compares one hourly sample with the previous one and records a transition when the derived offset changes. The evidence file therefore contains the transition instant, the offset before, the offset after, and the delta for the transitions found in this selected 2026 set.

Model one explicit recurring-meeting rule

The recurring-meeting evidence uses America/Vancouver as the reference zone and steps fifty-two weekly events pinned to a fixed local wall-clock time there. For each target zone it records the distinct offset differences, the minimum and maximum shift, and the spread across those fifty-two events.

What the selected evidence set demonstrates

The ten-zone file contains six zones that change offset during 2026 and four that do not. It includes northern and southern transition patterns, constant half-hour and quarter-hour offsets, and Chatham's moving forty-five-minute offset. Those are coverage examples inside the selected set, not a statistical sample of all zones.

What hourly sampling does not prove

The current evidence shows that hourly sampling captured the transitions present in these ten 2026 zone records. It does not establish that every current or historical IANA rule changes only on an hourly boundary, and it does not reconstruct years outside the generated file. The result also inherits the time-zone database bundled with the runtime used to generate it.

How to reproduce the evidence

Run the repository's time evidence generator for the same year and inspect the resulting zone records and recurringMeeting block. A matching runtime time-zone database should reproduce the offsets and transition records because they are derived rather than copied from prose.

How to apply one recorded result

Before using a figure, check the evidence year, the exact zone identifier, and whether the recurring-meeting anchoring rule matches the scheduling question. A correct value from this file can still be inapplicable if a different year, zone, or recurrence rule is being discussed.

First-party evidence and provenance

How we checked this

We derived every offset and transition from the runtime's own time-zone database by sampling the zone offset hourly across the calendar year, then modelled a weekly meeting pinned to a fixed local wall-clock time in a reference zone. The generator is in this repository and the evidence file is its output. For this guide we documented the generator's sampling and comparison procedure itself, including the hourly sampling interval and the whole-or-half-hour assumption it depends on.

Method: We derived every offset and transition from the runtime's own time-zone database by sampling the zone offset hourly across the calendar year, then modelled a weekly meeting pinned to a fixed local wall-clock time in a reference zone. The generator is in this repository and the evidence file is its output.
Environment: Node.js on a desktop workstation, using the bundled IANA time-zone data. No network call, no hard-coded offset table, and no user data.
Captured: September 20, 2026
Reviewed by: BeanNest Studio

Repository evidence artifacts:

tools/research-evidence/time/transitions-2026.json
tools/research-evidence/time/README.md