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history 
History of the International Date Line

     

Contents:

  • The circumnavigator’s paradox

  • The discovery of the date line

  • Some 17th-century proposals for a date line

  • The course of the date line before the Philippine adjustment

  • The Philippine adjustment of 1844/45

  • The Alaska adjustment of 1867 and the Samoa adjustment of 1892

  • The date line before and after the International Meridian Conference (1884)

  • The Kiribati adjustment of 1994/95

  • The location of the IDL according to the Pacific Islands Pilot

  • The location of the IDL according to some major 20th-century atlases

  • References

 


The circumnavigator’s paradox

What appears to be the earliest reference to the circumnavigator’s paradox is found in the works of the Syrian prince and geographer-historian Ismail ibn Ali ibn Mahmud ibn Muhammad ibn Taqi ad-Din Umar ibn Shahanshah ibn Ayyub al Malik al Muayyad Imad ad-Din Abu l-Fida (1273 - 1331). In his Taqwin al-Buldan (The ??? of the Lands), Abu l-Fida described how a traveller, depending on his dircetion of travel, would either lose or gain a day at the completion of his circumnavigation [Rudolf Wolf, Handbuch der Astronomie, Ihrer Geschichte und Literatur (Zurich, 1890), vol 1, pp. 465-466;].

Another early reference to the circumnavigator’s paradox is found in the works of the French scholar Nicole Oresme (c. 1325 - 1382). In his Traitié de lespere (which was also translated into Latin as the Tractatus sperae), Oresme presented a remarkable circling of the Earth by two imaginary travellers Jehan and Pierre (Johannes and Petrus in the Latin version) who set out to journey around the world along the equator in opposite directions at a speed of 30 degrees of longitude per 24-hour day. Jehan, travelling in a westward direction, would claim at the completion of his journey that it took him only eleven days and nights while Pierre , travelling in an eastward direction, maintained that it lasted thirteen days and nights. A third man, Robert, who had remained at the starting point, would however point out that only twelve days and nights had elapsed since both travellers had set out.

Oresme repeated this argument in his Quaestiones supra speram, a series of clarifications of questions based on the popular cosmographical treatise De sphaera by Sacrobosco, in which he renamed his travellers Plato and Socrates and the control Petrus and allowed both travellers a more leasurely pace of 14.4 degrees of longitude per 24-hour day. At the return of the philosophers at the starting point, Plato (the westward traveller) would have logged twenty-four days, Socrates (the eastward traveller) no less than twenty-six days, while Petrus saw the sun rise and set only twenty-five times.

Around 1377 Oresme wrote his Traitié du ciel et du monde, a French translation and commentary of Aristotle’s De caelo et mundo, in which he again discussed the circumnavigator’s paradox. Here the westward traveller is simply named A, the eastward traveller B and the control C. Each of both travellers is now assumed to cover 40 degrees of longitude per 24-hour day; A counting eight days for his circumnavigation, B ten days, while C only marks nine days on his calendar.

In order to resolve the circumnavigator’s paradox for future travellers, Oresme concluded his discussion of the imaginary journeys of Plato and Socrates in the Quaestiones supra speram with the observation:

‘From this it follows that if this [equatorial] zone were everywhere habitable, one ought to assign a definite place where a change of the name of the day would be made, for otherwise Socrates would have two names for the same day and the other [Plato] would have the same name for two days.’

 

The discovery of the date line

 

It was Antonio Pigafetta (c. 1490 - c. 1535), the Italian chronicler of the first circumnavigation of the world by the Portuguese explorer and navigator Ferdinand Magellan (c. 1480 - 1521), who first mentioned a peculiar incident that had occurred during the voyage: somewhere a whole day had apparently been lost. When Pigafetta, one of the eighteen survivors of the original 270-odd crew members who had set out from the Spanish port of San Lúcar de Barrameda in September 1519, nearly three years later sighted the Cape Verde Islands.

 

The story of the lost day experienced by Magellan’s crew was also transmitted in a different version by Pietro Martire d’Anghiera (1457 - 1526) in the 5th decade of his De Orbe Novo (1530). This passage was translated by Richard Eden in The Decades of the Newe Worlde or West India (1555) as:

 

‘And amonge other notable thynges by hym [Peter Martyr] wrytten as touchynge that vyage, this is one, that the Spaniards hauynge sayled abowt three yeares and one moneth, and the most of them noytynge the dayes, day by day (as is the manner of all them that sayles by the Ocean), they found when they were returned to Spayne, that they had lost one day. So that at theyr arryuall at the porte of Siuile beinge the seventh day of September, was by theyr accompt but the sixth day. And where as Don Peter Martyr declared the strange effects of this thynge to a certeyne excellente man [Gaspari Contarini of Venice (1483 - 1542)] who for his singular lernynge was greatly aduanced to honoure in his common welthe and made Themperours ambassadore, this woorthy gentelman who was also a greate Philosopher and Astronomer, answered that it coulde not otherwyse chaunce unto them hauynge sayled three years continually, euer folowynge the soonne towards the West. And sayde furthermore that they of owlde tyme obserued that all suche as sayled behind the soonne towards the West, dyd greatly lenghten the day.’

 

Peter Martyr’s lengthy discussions with Gaspari Contarini on this topic were summed up as:

 

‘Being much disquieted and touched with that case, I conferred with Gaspari Contarini (a man not meanly instructed in all kinds of literature), who was then ambassador with the Emperor for his famous commonwealth of Venice . Whereby we know (discussing the matter with divers arguments) that this strange report, never heard before, might very well be after this manner: This Castilian ship set sail from the Islands of Gorgades [Cape Verde Islands] towards the west, which way also the sun goeth. Thence it came to pass that having followed the sun, they had every day longer according to the quantity of the way they made, wherefore having perfited [encompassed] the circle, which the sun performeth in twenty-four hours towards the west, it consumed and spent one whole day, therefore it had fewer days by one than they who have that space of time kept one certain place of abode. But if the Portugal fleet, which saileth toward the east, should return again unto the Gorgades, continuing their course unto the east by this way and navigation, now first found and discovered to mortal men, no man would doubt, seeing they should have shorter days, having perfited the circle, but that twenty-four whole hours should remain unto them over and above, and so one whole day, wherefore they should reckon more by one. And so if either fleet, to wit, the Castilian and the Portugal, had set sail the same day from the Gorgades, and the Castilian had sailed toward the west and the Portugal had toward the east, turning stern to stern, and had returned to the Gorgades by these divers ways in the same space of time and at the same moment, if that day had been Thursday to the Gorgades, it had been Wednesday to the Castilian, to whom a whole day was consumed into longer days. But to the Portugal , to whom by shortening of the days one day remained over and above, the same day would be Friday. Let philosophers more deeply discuss this matter, we yield these reasons for the present.’

 

Nearly sixty years later, the same phenomenon was observed by the crew members of the fleet of the English explorer Francis Drake (c. 1545 - 1596), when in September 1580 they arrived back again in Plymouth after a long westward voyage around the world that had started in late 1577.

 

‘The 22 day [of September] we were in the height of the Canaries. And the 26 of Sept. (which was Monday in the iust and ordinary reckoning of those that had stayed at home in one place or countrie, but in our computation was the Lords day or Sonday) we safely with ioyfull minds and thankfull hearts to God, arrived at Plimoth, the place of our first setting forth, after we had spent 2 yeares 10 moneths and some few odde daies beside, in seeing the wonders of the Lord in the deep, in discouering so many admirable things, in going through with so many strange aduentures, in escaping out of so many dangers, and ouercomming so many difficulties in this our encompassing of this neather globe, and passing round about the world, which we haue related.’

 

In 1594 the Venetian trader Francesco Carletti (1574 - 1636) set out on a remarkable circumnavigation of the world in westward direction that lasted until the year 1606 and which he described in his Ragionamenti del mio viaggio intorno al mondo. Travelling without great haste via the Spanish dominions, crossing the isthmus of Panama and stopping over at Manila , he booked a passage for the Japanese port of Nagasaki in 1597. Upon his arrival there he observed:

 

‘And we found a difference in reckoning the days between us, who had come from the city of Manila , and the Portuguese who had come from that of Macao , an island of China . These Portuguese, having left Lisbon and navigated constantly eastward, had reached Japan as the furthest point of their journeying. During their voyage, the sun having risen for them constantly earlier, they had gained twelve hours of a natural day. We, on the contrary, having left the port of Sanlucar de Barrameda in Spain and navigated steadily westward and having lost daylight constantly because the sun kept rising later, had lost twelve hours. So when we discussed it with them, we found that we had reached a difference of one day. And when they said it was Sunday, we counted up to Saturday. Had I pursued my voyage around the entire world without having met those Portuguese, by the time of my arrival in Europe , whence I first had departed, I should have lost exactly a whole day of twenty-four hours.

For I, having moved constantly from the east toward the west, changing meridians and therefore making the day later for myself, would have encountered this difference of one day as caused, as I have said, by the later or earlier rising and setting of the sun in the diverse meridians, which continue changing daily for those who navigate toward the east and toward the west. And it is true that in the Philippine Islands on that same day when the Spaniards and their Church are celebrating Holy Saturday, those who are in Japan - that is, the Portuguese and their Church - are eating meat, because for them it is the day of the Resurrection. So that if they were moving swiftly enough to reach Manila the next day, as is said to have happened to some navigators, they would celebrate the same Easter or other solemnity twice. And if they were to arrive on the day when those people celebrate the feast, it would befall them to return on Holy Saturday. On the other hand, if those from Manila should set out on the day when they solemnize Christmas and reach the island of Macao , where the Portuguese are, they would find those others at the second feast of Saint Stephen, and would thus celebrate one and another solemnity on the same day. And if they were able to arrive on the day before Christmas by their count, they would be able to eat meat without having fasted on the preceding day.

And this suffices for knowledge of that occurrence, perhaps not better understood earlier because the world had not been circumnavigated in olden times as it now is travelled around by value and virtue of the two crowns of Castile and Portugal, who have showed the way, the former navigating toward the east and reaching China and Japan, the other toward the west and reaching these Philippine Islands, about one thousand mikes from the island of Macao in China, the residence of the Portuguese. Together, those two crowns have come to make a circle around the whole world ...’

Dutch circumnavigators of the world also had similar experiences. When Isaac le Maire (?? - 1624), after an arduous voyage around the southern tip of South America (named Cape Horn after the port of departure Hoorn ), finally reached the port of Batavia on Java in November 1616, he noted in his journal:

 

‘This [the confiscation of his ship and cargo by the authorities of the Dutch East India Company] was done on Munday the first day of November, after our reckoning, but upon a Tuesday the second of November by our Countrimens reckoning there. The reason of the difference of time fell out thus – as we sayled westward from our own Countrey, and had with the Sun compassed the Globe of the World, we had one night, or Sun-setting less then they. [...] That weeke we lost the Tuesday, leaping from Munday to Wednesday, and so had one weeke of six dayes.’

 

Some 17th-century proposals for a date line

In 1612 the French historian Nicholas Bergier (1567 - 1623) published a work entitled Archemeron [Le point du jour], ou traicté du commencement des jours et de l’endroit où il est étably sur la terre in which he proposed to adopt the meridian opposite to the prime meridian of the renowned Flemish-German cartographer Gerard Mercator as a suitable date line.

Apparently unaware of Bergier’s earlier proposal, the Louvain humanist and scholar Erik de Put (Erycius Puteanus, 1574 - 1646) published a work in 1632 in which he argued for the adoption of a prime meridian running through Rome, which, in honour of the ruling Pope Urban VIII, he proposed to name the Circulus Urbanianus. The meridian opposite to that of Rome he named the Linea Archemerina and marked the line where the calendar date changed.

Puteanus pointed out that in order to be useful a date line should pass only over water without crossing any land and he conceded that his date line would have to make an eastward excursion at the latitude of New Albion in order to satisfy this condition.

His proposal was vigorously attacked by Giacomo Micalori (1570 - 1645), a professor of theology and philosophy at Urbino, who described it as mancus, supervacaneus, imaginarius et, ut omnia dicerentur, nullus [???]. Puteanus countered the objections from the fool from Urbino in a work published in the following year that in turn was criticised by Micalori in 1635. Though Puteanus received support from his friend Godfrey Wendelinus and others, his proposal found little favour among cartographers with the exception of his friend Michel-Florent van Langren (1598 - 1675), who around 1645 (or later) published a 52½-cm terrestrial globe that depicted his meridians.

The course of the date line before the Philippine adjustment

Early 19th-century charts and globes never seem to have depicted the course of the date line across the surface of the Pacific but in 1830 the German astronomer Heinrich Wilhelm Matthias Olbers (1758 - 1840) gave the following verbal description of its approximate position:

 

‘Beyläufig wird sie jetzt, vom Südpol kommend, östlich von Neuseeland und Neuholland [Australia] entfernt bleiben, sich dann zwischen den Carolinen und Neuguinea hindurch nach Westen biegen, die Philippinen und Marianen einschliessen, südöstlich von den Japanischen und Kurilischen Inseln, und südlich von den Aleuten nach der Nordwestküste von America streichen; diese Küste zwischen den Niederlassungen der Anglo-Amerikaner und der Russen durchschneiden, und nicht weit östlich von diesen Russischen Colonien nach dem Nordpol laufen. Dies ist ungefähr die jetzige Richtung und Figur der Linie, auf der derselbe Tag zugleich anfängt und aufhört. Westwärts von dieser Linie zählt man als Datum und Wochentag einen Tag mehr, als ostwärts.’

 

In 1830 the German sea-captain G. Wilcke from Stettin in Prussia (now Szczecin in Poland) published a pamphlet entitled Abhandlung ueber die Annahme eines allgemeinen Kalendermeridians in which he proposed to adopt the meridian passing through the middle of the Bering Strait (which he determined to be 169º 01' West of Greenwich) as a suitable date line. Wilcke’s proposal was reviewed for the Astronomische Nachrichten by Olbers, and although he granted that the author showed good sense in choosing a meridian that passed mostly over water and bisected only a few island groups, he was of the opinion that a fixed date line was only of limited use and would be difficult to implement in an age when one could not even agree on the choice of a common prime meridian.

The Philippine adjustment of 1844/45

When the British ex-buccaneer, sea-captain and explorer William Dampier (1651 - 1715), during his travels across the globe from 1679 to 1691, weighed anchor after his stop-over on the island of Mindanao in the Philippines in January 1687, he noted in his journal:
 

It was during our stay at Mindanao , that we were first made sensible of the change of time, in the

course of our Voyage. For having travelled so far Westward, keeping the same Course with the

Sun, we must consequently have gained something insensibly in the length of the particular Days,

but have lost in the tale, the bulk, or number of the Days or Hours. According to the different

Longitudes of England and Mindanao , this Isle being West from the Lizzard, by common

Computation, about 210 Degrees, the difference of time at our Arrival at Mindanao ought to be

about 14 Hours: And so much we should have anticipated our reckoning, having gained it by bearing

the Sun company. Now the natural Day in each particular place must be consonant to itself: But this

going about with, or against the Sun’s course, will of necessity make a difference in the Calculation

of the civil Day between any two places.

Accordingly, at Mindanao , and all other places in the East-Indies, we found them reckoning a Day

before us, both Natives and Europeans; for the Europeans coming eastward by the Cape of Good Hope ,

in a Course contrary to the Sun and us, where-ever we met they were a full Day before us in their

Accounts. So among the Indian Mahometans here, their Friday, the Day of their Sultan’s going to

their Mosques, was Thursday with us; though it were Friday also with those who came eastward

from Europe . Yet at the Ladrone Islands , we found the Spaniards of Guam keeping the same

Computation with our selves; the reason of which I take to be, that they settled that Colony by a

Course westward from Spain : the Spaniards going first to America , and thence to the Ladrones

and Philippines .’

As explained by William Dampier, the erratic course of the date line across the waters of

the Pacific Ocean was the result of the way that the Pacific region had been explored and

colonised by the various European powers during the 16th and the 17th century. In 1493 Pope

Alexander VI issued a bull in which the meridian line located 100 leagues west of the Cape

 

Verde Islands would divide the spheres of influence of the Spanish crown (westwards of

the demarcation line) and the Portuguese crown (eastwards of the same line). The

demarcation line was moved to 370 leagues west of the Cape Verde Islands in the following

year by the Treaty of Tordesillas, sanctioned by Pope Julius II in 1506.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

European explorers who approached the Pacific Ocean by sailing to the east such as the Portuguese, and in their wake the Dutch, the English and the French, naturally kept their ship’s journals and diaries according to the day count of their home land and this was of course also adopted by the colonists who settled along the Asian perimeter of the Pacific Ocean.

 

However, the colonisation of the Pacific Ocean by the Spanish occurred from the opposite direction and more specifiically from the Spanish possessions in America . The Philippine archipelago was discovered in March 1521 by Ferdinand Magellan and Spanish dominion over the islands was first firmly established in 1565 by Miguel López de Legazpi (c. 1510 - 1572), the conquistador and first Spanish governor general of the Philippines . He had been equipped with five ships by Luis de Velasco, the viceroy of New Spain, and left Acapulco in 1564. In April 1565 he reached Cebu, one of the southern islands of the archipelago, and founded the first Spanish settlement on the site of modern Cebu City . In 1570 he sent an expedition to the northern island of Luzon and in the next year he founded the city of Manila , which became the capital of the new Spanish colony and Spain ’s major trading port in East Asia .

 

Most of the shipping from the Philippines to Spain went over the Pacific Ocean to the Mexican port of Acapulco , was transported over land to the port of Veracruz , and then shipped to Spain . In order that the Spanish ships crossing the Pacific Ocean between the Philippines and the Spanish America’s would not have to adjust the dates in their journals whenever they sighted land, the Philippines observed the same day count as that of the Spanish America’s.

The Philippine tradition of counting the days according to the American reckoning could sometimes fool the unwary traveller. In 1590 the Spanish historian José de Acosta described the following in his Historia Natural & Moral de las Indias :

‘It happened to Father Alonse Sanches [...], that parting from the Philippines, he arrived at Macao, the second day of Maie, according to their computation, and going to say the Masse of S. Athanasius, he found they did celebrate the feast of the invention of the Holy Crosse, for that they did then reckon the third of Maie.’

 

During the early 1840’s the commercial interests of the Philippine Islands turned more and more away from the Spanish America’s (which for a large part had severed their relations with the mother land Spain) and trading with the Chinese mainland (engendered by the ignominious but lucrative Opium Wars), the Malay peninsula, the Dutch East Indies and Australia became increasingly important.

In order to facilitate communication and trading with its western and southern neighbours, the secular and religious authorities of the Philippines agreed that it would be advantageous to abolish the American day reckoning and adopt the Asian day reckoning.

This was achieved in 1844 when Narciso Claveria, the governor general of the Philippines , issued a proclamation announcing that Monday, 30 December 1844, was to be immediately followed by Wednesday, 1 January 1845.