Understand it,
teach it and cite it.

A lesson in three steps

1. Cross the line, change the date. Show the two calendars on the homepage. Ask students what happens to the date when crossing westward and when crossing eastward.
2. A specific decision. Read the Philippines story: who decided, which date was skipped and which document supports it?
3. A map with limits. Compare two outlines. Separate documentary claims from reconstructed routes.

A classroom map

A real Pacific base map with the 180° meridian and approximate reference points. The meridian alone is not the date line. Small islands may be absent at this scale.

Locate Samoa, Kiribati and the Philippines. Sketch an illustrative route consistent with their calendar histories. Do not describe it as a legal boundary.

Natural Earth 1:110m coastline, public domain. Atlas reference design, revision 7. Historical outlines retain their own provenance and are not assigned a new licence here.

For journalists and researchers

Start with the document supporting the claim. Library entries distinguish verification, research use and rights. A recorded reference is not evidence of a complete reading.

Citing this version

Evaristo Babé, The Date Line Atlas, revision 7 prototype, 2026. Include the page title, access date and its status as an unpublished local version. A permanent URL will be added once available.

What an outline cannot establish

A calendar change may be documented while its ocean route remains approximate or unknown. Cite civil-date evidence and geometric provenance separately.