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The date on the parchment

The bull bears the formal date 4 May 1493, at St Peter's in Rome. Papal-chancery evidence shows that this second Inter caetera was in fact prepared and expedited in June.

Nothing demonstrable changed on 4 May. The revised bull was expedited in June, reached Spain before a certified copy was made at Barcelona on 19 July, and that copy was sent to Columbus on 4 August.

The line, and what came with it

Alexander VI granted Ferdinand and Isabella and their heirs and successors as kings of Castile and León jurisdiction over islands and mainlands found or to be found westward and southward beyond a pole-to-pole demarcation line.

That line was described — awkwardly — as 100 leagues 'towards the west and south' from any of the islands commonly called the Azores and Cape Verde, a formula that could not be plotted as one unambiguous modern longitude.

Lands already in the actual possession of a Christian ruler by Christmas 1492 were excluded from the grant.

The conditions attached

The bull ordered the monarchs to send qualified instructors in the Catholic faith, and prohibited unauthorised travel or trade beyond the line under threat of excommunication. Columbus was praised by name, and his first voyage's reported discoveries supplied the immediate setting.

The first Inter caetera, formally dated 3 May, had granted only lands discovered by Castilian agents and safeguarded conflicting Christian rights more generally. After receiving it, Ferdinand and Isabella sought a more favourable replacement.

Documentary scholarship traces the revised provisions to those Castilian requests, and finds no evidence that Alexander acted as an impartial referee.

5 September 1494, at Setúbal

At Setúbal on 5 September 1494, King John II of Portugal formally ratified the agreement negotiated at Tordesillas. Spain's Ministry of Culture identifies the surviving document as the Portuguese confirmation and records the same date and place.

Ferdinand, Isabella and Prince Juan — whose signature the treaty expressly required — had already ratified at Arévalo on 2 July, so John's act completed the monarchs' approvals. The treaty had allowed 100 days from 7 June.

What the two crowns had agreed

Islands and mainlands east of a pole-to-pole line 370 leagues west of the Cape Verde islands went to Portugal; those west of it went to the rulers of Castile and their successors.

Both sides bound themselves not to send voyages for discovery, trade or conquest into the other's sphere, and to surrender discoveries made on the wrong side.

The treaty also planned a joint technical expedition — two or four caravels meeting at Grand Canary within ten months — to locate the line.

A line nobody could find

The text expressed no longitude at all, did not specify which Cape Verde island supplied the starting point, and contemporary navigators could not determine longitude reliably. The familiar 42°30′ W is a later reconstruction, and published reconstructions range roughly from 42° to 50° W.

The planned definitive survey was never achieved.

The two originals ended up across the border from each other: the Portuguese-language original is in Seville, the Castilian-language original in Lisbon.

9 February 1498

The art historian Pietro C. Marani identifies 9 February 1498 as the unveiling of Leonardo's completed Last Supper in Milan.

The date is tied to Luca Pacioli's dedication of De divina proportione, which praised the Last Supper as an accomplished work. That establishes the painting was complete by then — not that Leonardo applied a final brushstroke that day.

Treccani dates Pacioli's dedicatory letter to 8 February; the official museum gives a working range ending at the beginning of 1498, and UNESCO dates the work 1495–1497.

Where it was, and who ate under it

The finished painting covered the north wall of the Dominican monastery's refectory at Santa Maria delle Grazie, where the friars ate, prayed and meditated. It measures 460 by 880 centimetres.

Ludovico Sforza had commissioned the decoration while reshaping Santa Maria delle Grazie into a celebration of Sforza power and a family mausoleum.

Painted on dry plaster

Leonardo did not use true fresco. The pigments sat over a preparatory layer instead of being absorbed into wet plaster, which left him free to keep revising.

The official museum classifies the work as dry wall-painting and attributes its deterioration chiefly to that technique and to imperfect environmental conditions.

Decay was being observed by 1517.

13 September 1500

On 13 September 1500, Pedro Álvares Cabral's squadron arrived at Calicut, having sailed from Anjediva after about two weeks there.

Six vessels were sailing together, not nine: five carracks commanded by Cabral, Sancho de Tovar, Nicolau Coelho, Simão de Miranda de Azevedo and Nuno Leitão da Cunha, plus Pero de Ataíde's caravel São Pedro.

The fleet had left Lisbon on 9 March with thirteen vessels, and first reached the Indian coast on 22 August.

What they had come for

Manuel I had instructed Cabral to establish diplomatic and commercial relations with Calicut, the expedition's principal Indian destination. Aires Correia, the royal factor, held responsibility for the fleet's commercial business and was to manage the projected trading post.

Two Gujarati seamen supplied by the king of Malindi had guided the squadron across the final part of the voyage.

Then nothing moved

Initial meetings with the Zamorin's side followed, but negotiations dragged and the Portuguese ships stayed unloaded through the early impasse.

Arrival did not establish a stable Portuguese trading regime.

The attack on the Portuguese factory, the seizure of merchant ships and the bombardment of Calicut all came in December, not in September.

The date on this entry is not supported

No scholarly or primary source consulted supports 7 November 1502 for these events. Encyclopaedia Iranica consistently places the battle and the proclamation in 1501, and the listed date appears to derive from unsourced ruler lists copied online.

A Safavid chronicle composed in 1554, reporting testimony from several witnesses, gives 1 Jumada II 907 — 22 December 1501. It is the only narrative source offering an exact day, and it was written decades after the fact.

Sharur, and then Tabriz

In 1501 Ismail's Qizilbash army decisively defeated the Aq Qoyunlu ruler Alvand at Sharur in the Aras valley, breaking Aq Qoyunlu power in Azerbaijan. He had mobilised 7,000 Turkman tribesmen against a force more than four times that size.

Shortly afterwards he entered Tabriz, proclaimed himself shah, had coins struck in his name and made the city his capital. There he also decreed Shiism the official faith of the new realm.

He was fourteen.

Disciples, not only soldiers

The Qizilbash were predominantly Turkmen tribal disciples whose loyalty to the Safavid spiritual leader supplied Ismail's fighting force; the relationship was framed as that of a Sufi pupil to a sacred master. The movement and its distinctive red headgear had developed under earlier Safavid leaders, especially his father Haydar.

Husayn Beg Shamlu, a leading Qizilbash figure, was afterwards appointed Ismail's vicegerent and commander-in-chief.

A Safavid shah now held Azerbaijan and an officially Shiite state had begun — though much of Iran remained unconquered.

12 February 1502, at Seville

At Seville on 12 February 1502, Ferdinand of Aragon and Isabella of Castile jointly issued a royal pragmatic ordering the remaining Muslims of Castile and León to leave their realms by the end of April.

It applied to Muslim males older than fourteen and females older than twelve — an age rule that could split a household. An estimated 17,000–20,000 people were affected.

It was issued by both monarchs, not by Isabella alone.

A choice that was not one

The formal wording ordered expulsion rather than commanding baptism. But departure was tightly constrained, and restrictions and the danger of losing homes and livelihoods made conversion the realistic option for most families.

The decree justified expulsion by alleging that practising Muslims might draw recently baptised Muslims back to Islam, explicitly analogising the supposed danger to earlier Jewish influence on conversos.

Mass baptisms after the Granada rebellions of 1499–1501 had left the monarchy fearing exactly that; by September 1501 it had decided that Castile's other Mudéjars must accept baptism or go.

What had happened by April

Implementation ran through local proclamations and baptisms. A Valladolid study finds that by April some converted voluntarily, but most did so against their will.

In Valladolid, baptism replaced Arabic personal names with Christian ones: Farax Alcalde became Diego Alcalde, while his brother Mahomad became Bernaldo de León.

The decree covered Castile and León only. The Crown of Aragon, where Ferdinand had promised not to force conversion, kept legally practising Muslim communities for another generation.

October 1503, in the margin of a Cicero

In October 1503, the Florentine chancery official Agostino Vespucci wrote a marginal note in his copy of Cicero's Epistolae ad familiares — a 1477 edition — comparing Leonardo da Vinci's practice with that of the ancient painter Apelles.

Reading Cicero's account of Apelles leaving part of a Venus unfinished, Vespucci recognised the same quality in Leonardo and listed contemporary examples.

Among them he named the 'head of Lisa del Giocondo'.

What the note proves, and what it does not

It is the earliest surviving contemporary documentary record of Leonardo working on a portrait of Lisa del Giocondo, and the Louvre identifies that work with the painting now called the Mona Lisa.

Vespucci used neither title, Mona Lisa nor La Gioconda, and did not describe the finished composition. The identification is strongly accepted by the Louvre and most specialists, but the note alone cannot prove every step in the panel's provenance.

The month dates the annotation and confirms the work was under way by then; it is not necessarily the month Leonardo first touched brush to panel.

Three projects in a few lines

The same note mentions Leonardo's Saint Anne and his agreement with Florence's gonfalonier concerning work for the Great Council Hall, now associated with the Battle of Anghiari project.

Armin Schlechter found the annotation while cataloguing Heidelberg University Library's incunabula, and the discovery was first published in May 2005.

The Louvre's current date range for the painting is 1503–1519.

All Saints' Day, 1 November 1503

On 1 November 1503 the cardinals completed the second papal conclave of the year and elected Cardinal Giuliano della Rovere, bishop of Ostia. He accepted and took the name Julius II; the Holy See numbers him the 216th pope.

All thirty-eight participating cardinals attended the morning Mass, signed the electoral capitulations and proceeded to the formal scrutiny. Johann Burchard's contemporary-derived tally gives della Rovere thirty-six first-choice votes — nearly unanimous, rather than unanimous.

A conclave measured in hours

The conclave had opened on 31 October and effectively settled on della Rovere that same evening. The formal election followed the next morning after only a few hours of conclave business.

Pius III had died on 18 October after a twenty-six-day pontificate, creating the second papal vacancy of the year. The September conclave had elected him; this one elected Julius.

Arranged before the doors closed

Della Rovere had secured broad support beforehand by reaching understandings with former opponents. The French-backed candidate Georges d'Amboise had been neutralised, and Cesare Borgia reached an agreement with him, after which Spanish cardinals aligned with the future pope.

Niccolò Machiavelli was in Rome on diplomatic assignment and reported the election and its political implications to Florence.

The election was on 1 November; the coronation followed on 26 November.

Not something that happened in 1503

This is not a single shipment or occurrence. It is a retrospective total reconstructed from registrations of American bullion imported into Spain between 1503 and 1660: approximately 16,000,000 kilograms of silver and 185,000 kilograms of gold.

What did happen that year was administrative. On 20 January, at Alcalá de Henares, Ferdinand and Isabella issued a royal provision establishing the Casa de la Contratación in Seville and promulgating its first ordinances.

Where the paper was, and where the ships were

The Casa registered and supervised Indies commerce, and its surviving records became the archival basis for the whole series. Seville was the administrative destination and the place of registration.

Seville is inland. Another account identifies Sanlúcar de Barrameda, at the mouth of the Guadalquivir roughly 80 river kilometres away, as the port where the bullion arrived from the Atlantic.

How solid the numbers are

The economic historian Earl J. Hamilton reconstructed the import series from Casa records. The underlying registrations combined gold and silver by monetary value, and his division of the total into weights of each metal involved estimates that a later economic-history review calls partly speculative.

Official registrations also omit contraband and other unrecorded flows, so the figures are recorded-import estimates or lower bounds.

They are not the same thing as total American mine production, or as bullion retained by the Spanish Crown.

25 April 1507, at Saint-Dié in Lorraine

The first edition of the Cosmographiae Introductio bears the publication date 25 April 1507 and was issued at Saint-Dié by the humanist circle known as the Gymnasium Vosagense.

The book was one piece of a three-part project. The others were a twelve-sheet wall map drawn by Martin Waldseemüller and a set of globe gores, and all three introduced the name "America."

Where the new name actually sat

On the main map, "america" was printed on the southern landmass. It was not yet the collective name of both modern American continents.

The accompanying text justified the coinage as a feminine form derived from the Latinized Americus, crediting Amerigo Vespucci as the supposed discoverer of a fourth part of the world.

Who wrote that text is disputed. Most specialized scholarship credits the humanist Matthias Ringmann, while older cataloguing and some accounts assign it to Waldseemüller.

An ocean with no known source

The map showed South America separated from Asia in a way that implied an intervening Pacific Ocean — years before Balboa or Magellan reached that ocean from the European side.

The Library of Congress says the geographic source for this remains unknown.

Waldseemüller reported a print run of a thousand copies. One wall map survives, and the Library of Congress completed its US$10 million purchase of that copy in 2003.

May 1508, not December

Michelangelo signed the ceiling contract on 8 May 1508. Two days later he received a 500-ducat advance and recorded in a memorandum that he was beginning work on the vault that day.

The December 1508 date attached to this event is not supported by the strongest sources consulted.

The commission existed because a long crack had opened in the chapel ceiling in May 1504, probably because nearby construction disturbed the building. Bramante fitted tie rods, but the damage to the older starry-sky decoration led Julius II to commission a replacement.

Formal start and first brushstroke are not the same day

What Michelangelo began on 10 May was the project. The Metropolitan Museum dates the physical fresco campaign to late summer 1508.

Design, material preparation, plastering and scaffolding stood in between. The exact day pigment first went onto wet plaster is unknown.

Twelve Apostles become nine Genesis scenes

The contract's initial program called for twelve Apostles in the pendentives and ornamental decoration elsewhere. Michelangelo persuaded Julius II to abandon that limited scheme and give him broad control of the program.

What he built instead was centred on nine Genesis narratives, over a documented working span of 1508 to 1512.

He did not work alone. The British Museum records that Michelangelo called the painter Francesco Granacci to Rome in 1508 to assist.

About nine in the morning, 3 February 1509

At about 09:00 on 3 February 1509, Francisco de Almeida signalled his ships to advance on the fleet lying off Diu, on Gujarat's coast. He had assembled the force after Hussein al-Kurdi and Malik Ayyaz beat a Portuguese squadron at Chaul the year before and killed his son Lourenço.

The Portuguese closed with Hussein's Mamluk vessels, pinned individual ships between several of their own, and boarded them. Hussein's flagship and most of his squadron were lost.

Gunboats, rescue craft, and a chain across the harbour

Malik Ayyaz brought Gujarati gunboats out to assist Hussein, while smaller Malabar vessels pulled men from the water and carried supplies. Hussein himself escaped.

After the last Egyptian vessel was beached, boarded and burned, Ayyaz withdrew his surviving forces behind Diu's harbour chain. The Portuguese ships stayed outside it, facing the chain, shore guns, soldiers and the Gujarati craft still afloat.

Almeida sails away without the port

Almeida wanted the surviving Egyptians handed over for execution. Ayyaz refused.

Almeida negotiated instead for the Portuguese prisoners taken at Chaul, obtained their release, and left without capturing Diu. Ayyaz still held the city and still had a functioning Gujarati fleet.

How many Portuguese died is unclear. The familiar figure of 40 is probably a dropped zero — the underlying chronicle opens with 1,600 personnel and later accounts for only 1,200 — and Cameron Winter argues that 400 fits the text better.