# Time Zone Transition History

Dated offset and daylight-saving transitions, plus recurring future rules, from the same IANA release.

## Contents

| File | Records | Format |
|---|---:|---|
| transitions.json | 23,021 | JSON array |
| recurrences.json | 340 | JSON array |

The download contains the populated data, a field dictionary, source metadata, reuse terms, a change log and file digests. It contains no scripts, libraries, executables or conversion tools.

## Coverage

All explicit transitions emitted by the host zic compiler in fat TZif format from this release; no user-selected date cutoff. Canonical zones are stored once. Future recurrence remains declarative data rather than an arbitrarily bounded expansion. Pre-1970 coverage is uneven in tzdb; an absence of records does not establish no historical change.

## Sources and dates

- [IANA tzdb](https://data.iana.org/time-zones/tzdata-latest.tar.gz): 2026c. Retrieved 2026-09-08T02:02:47.183841+00:00.

## Read the data

JSON tables are arrays of records. GeoJSON files are FeatureCollections, with data fields under each feature’s properties. `data-dictionary.json` defines the fields, units, nulls and observed types. `metadata.json` supplies primary keys and source hashes. Preserve identifiers as text and distinguish missing values from zero.

## Example record

This is an actual record from the data. For map layers, the example shows properties; the downloaded GeoJSON also contains the complete geometry.

```json
{
  "zone_id": "Africa/Abidjan",
  "at_unix_seconds": -1830383032,
  "at_utc": "1912-01-01T00:16:08+00:00",
  "utc_offset_seconds_after": 0,
  "is_dst_after": false,
  "abbreviation_after": "GMT"
}
```

## Reuse terms

Public domain. IANA Time Zone Database contributors.

[Publisher terms](https://www.iana.org/time-zones/tz-link). License notices are included where supplied.

## Tracking changes

Compare (zone_id, at_unix_seconds), pre-first types, and tail recurrence on each IANA release.

This publication is a snapshot. No automatic refresh is scheduled. New imports must preserve their source version, retrieval date and hashes, then publish a new Arcomm revision.

## Download

[Download the file](/files/a3ac609b91f80cba43e22c5c8ef0013162a5f6a66cd33ef29530d50fe15c2c3e)

SHA-256: `a3ac609b91f80cba43e22c5c8ef0013162a5f6a66cd33ef29530d50fe15c2c3e`

Size: 244301 bytes.

## Revisions

[Revision history](/agent/docs/time-zone-transition-history/history)