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The Date Line AtlasStories, maps and documents
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Documents · Method · Corrections

How we check
these stories.

A law can tell us when an island changed date. A map shows how the line was drawn. We consult both and explain what each one tells us.

Evidence checked · 23 October 2026

The sources behind each outline

Choose a place to see the evidence and its limits. The dates on the outlines include calendar changes, map editions and approximate periods. They are not fourteen official versions of a worldwide boundary.

Pitcairn: Saturday at sea, Sunday ashore

Island in the South Pacific.

Pipon records a one-day disagreement during his visit on 17 September 1814: the ships kept Saturday, while John Adams believed it was Sunday the 18th.

We consulted a transcription of the account. This passage gives no order to change the calendar and draws no boundary around the island. Our circle is an explanatory symbol.

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The Philippines: the decree that removed 31 December

Archipelago in Southeast Asia.

Clavería’s decree of 16 August 1844 ordered Monday 30 December to be followed by Wednesday 1 January 1845. Benko reproduces the Spanish text.

The reproduction comes from a copy certified in 1889. We have not inspected the 1844 original. IANA assumes the Marianas changed at the same time; this does not establish the full corridor drawn on our map.

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Tahiti: evidence pointing to late 1846

Polynesian island in the South Pacific.

Kape and Koenig place a Tahitian calendar change in late 1846, in their study of a May 1847 letter from Pomare IV. We therefore do not treat 1847 as an established date of change.

This is a 2013 study, not the original order. A search of the official bulletin’s 1842–1850 index did not locate that order. The exact date, affected islands and shape of the detour remain unestablished.

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Alaska: a transfer and two ways of counting dates

Territory in northwestern North America.

The 1867 treaty documents Alaska’s transfer. The Admiralty notes explain how the change of date was reflected in the line near the Bering Strait.

The treaty describes territorial boundaries; it does not establish a worldwide Date Line. A local calendar account must identify the ceremony date, calendar used and place where it was recorded.

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Samoa: the order to repeat Monday

Polynesian islands in the South Pacific.

The proclamation of 16 June 1892 ordered the old calendar’s Tuesday 5 July to be called Monday 4 July. It appeared in the Samoa Times on 18 June, page 3.

The order establishes the calendar instruction. The 2 July newspaper announces celebrations for the second Monday. Neither source fixes every turning point of an oceanic line.

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Cook Islands: a two-day Christmas

The Cook Islands are a Polynesian archipelago.

The 1899 Christmas Day Act directed that New Zealand’s 25 and 26 December be counted as one date, 25 December, in the Cook Islands. Tuesday the 26th would follow.

The law is reproduced on page 20 of the 1900 parliamentary report. It does not establish that Niue followed the same order. The outline’s 1900 label refers to a map publication, not the date of this law.

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Kwajalein: why we show 1969

Kwajalein is an atoll in the Marshall Islands: a coral ring with islands around a lagoon.

IANA uses 1969 for an earlier Kwajalein change, but its own comment says it retains that date pending better evidence. This is not a verified 1969 government order.

The date remains approximate in this reconstruction. A contemporary order or local record of the change is needed to establish it.

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Kwajalein: the missing Saturday of 1993

Kwajalein is an atoll in the Marshall Islands: a coral ring with islands around a lagoon.

The Associated Press report quoted by IANA describes a Friday-to-Sunday jump in August 1993. Its time-zone record skips Saturday 21 August in Kwajalein.

The change concerns Kwajalein. It must not be extended to all the Marshall Islands or used to date the beginning of the earlier arrangement.

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Kiribati: the missing day and the corrected record

Kiribati is a country made up of several Pacific island groups.

In 2018, Paul Eggert corrected an IANA data-entry error: the eastern islands had skipped 31 December 1994, not 1 January 1995.

A separate question remains: Hay (2001, p. 32) reproduces a local 4/5 January notice and cites Cabinet Memo No. 36/94, MHARD 5/16. The original notice is needed to establish whether it describes delayed implementation. The IANA error itself is explained.

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Samoa: the map attached to the law

Samoa and Tokelau are two Polynesian island groups.

Section 5 of the 2011 Act moves the line east of Samoa and specifies 171° west. Its schedule shows the former line in red and the new line in blue. We have checked the image.

The map is on PDF page 5, after the schedule heading on page 4. The Act concerns Samoa; it does not legislate for Tokelau or American Samoa. Our outline remains a simplification.

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Admiralty maps: what changed on paper

The Admiralty notes distinguish the US chart of 1899, the British chart of 1900 and the 1910 revision, reported in 1911. That revision removed the bend around Morrell and Byers, islands no longer shown on its charts.

The text is dated November 1921 and was reprinted in 1930. It supports neither an additional 1919 revision nor the received B03 variant’s “after c. 1924” date. We retain that variant as archive material, not as a civil change.

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01

Civil observance

What date was used in a territory? We look for the decision, its effective date and the people or places it covered.

02

Published map

Who drew it, and when? A map can preserve an older convention or disagree with another map from the same year.

03

Our reconstruction

What can we draw from these documents? The complete outlines remain provisional. Where information about a section is missing, we say so.

Sources to inspect

  1. International Date Line Act 2011

    Official Samoa text. Sections 4–8 establish standard time, the date change and its effects. See the Samoa prototype for precise references.

    Attorney General of Samoa ↗
  2. The International Date Line

    Reference retained from the supplied package. This page could not be retrieved during this review. The basic explanation is supported by NOAA.

    USNO ↗ · NOAA ↗
  3. Notes on the History of the Date or Calendar Line

    Hydrographic notes, November 1921, reprinted in 1930, pp. 385–388. Map revisions are evidence about cartography; they do not automatically date civil changes.

    Internet Archive ↗
  4. A History of the International Date Line

    R. H. van Gent · Utrecht University

    Utrecht ↗

Three editorial states

Verified
The specific claim has sufficient evidence. This never certifies a whole map by association.
Disputed
Evidence or interpretations conflict.
Pending
The required document, locator, geometry or rights check is missing.

Files and reuse

The original SVG and GeoJSON are available in this local preview for review. Public redistribution requires checking rights by layer and agreeing a licence for the atlas’s own data. We do not yet offer the package as an open-data release.

Inspect original GeoJSON ↓

Corrections · 21 October 2026

Suggest a correction through the existing contact form →

Initial selection · 10 bilingual pieces

The source behind each discovery

C06 · Technical record checked

Kiribati skipped a New Year’s Eve

IANA records show Kanton and Kiritimati jumping from 30 December 1994 to 1 January 1995. The change affected eastern Kiribati, not the whole country.

The historical file retains a discrepancy about local implementation in January 1995. The software rule alone does not settle that question.

IANA Time Zone Database · australasia ↗
Pacific/Kanton and Pacific/Kiritimati, 1994 Dec 31

Link to this discovery ↗