On Wednesday 2 September 1752 Britain and its colonies went to bed, and woke on Thursday 14 September. Rome had made the same jump 170 years earlier; Russia waited until 1918, Greece until 1923. This map shows when each country switched to the Gregorian calendar, alongside three other great switches: which side of the road to drive on, the metric system, and votes for women. It is a story of the world slowly agreeing on things, and of the stragglers.
Every country on this map once ran its own way. Each kept its own calendar, chose its own side of the road, weighed in its own pounds, ells and catties, and decided for itself whether women had a say. Over four centuries most of them converged on the same answers, often in waves: Catholic Europe's calendar in 1582, the Protestant states around 1700, the Orthodox east after the First World War; driving on the right across the 1920s and again in the 1960s and 1970s, as Britain's former colonies in West Africa joined their French speaking neighbours; votes for women in a rush after each world war.
The dates here come from the tables in English Wikipedia's articles on each switch, read cell by cell and matched to today's borders. For the calendar the main source is a list of 146 historic areas, from Carinthia to Kovno, each with its last old style day and first new style day. Where the articles disagree, or a historical state has to stand in for a modern one, the map says so when you click. Press play to watch the switches roll across the world, or pick a country.
Countries are today's (Natural Earth); a historical state is drawn with the modern country that covers most of it, and the popup says when that is a stand in. Sub-national detail (Dutch and Belgian provinces, Swiss and Austrian cantons and states, Canadian provinces, Australian states, Alaska, Okinawa) is drawn where the sources give it. Calendar: "List of adoption dates of the Gregorian calendar by country", checked against the adoption tables in the Gregorian and Julian calendar articles and the prose of "Adoption of the Gregorian calendar". Colour: the year the whole of today's country had switched; paler where only part had. Driving side: "Left- and right-hand traffic". Metric: "Metrication". Votes: "Women's suffrage". All Wikipedia, CC BY-SA 4.0.
Seen as curves, each switch has its own rhythm. The calendar moved in great religious blocs: by 1600, 33 of today's countries were on it, most of them Spain's and Portugal's colonies in the Americas, counted with them; by 1800 it was 49; the Orthodox and Asian switches of 1873 to 1929 brought it to 80. Votes for women went from almost nowhere in 1900 to half of today's countries by 1951 and 170 by 1970. Metrication crept along through the nineteenth century, 29 countries before 1900, then surged after the Second World War. Driving on the right is the only one with a large group that never joined: 54 countries, with 36% of the world's people, still keep left.
How fast the world switched
Share of today's 197 countries, or of today's world population, that had made each switch by each year. Hover or tap for values.
The calendar and metric lines count only the countries the sources date: 82 countries for the calendar (including 27 former colonies I date by their colonial power) and 73 for metrication. Most of the others use the Gregorian calendar and have mandatory metric laws today, but the tables give no year, so these lines stop short of the top. Population is today's, so the lines show how much of today's world had switched, not the share of people alive at the time. Driving: where the table gives no date of switch, today's side is assumed throughout.
The Julian calendar, Julius Caesar's, gives every fourth year a leap day. That makes its average year about eleven minutes too long, and by the sixteenth century the calendar had drifted ten days from the seasons that set the date of Easter. Pope Gregory XIII's reform of 1582 removed the drift in one go: in Spain, Portugal, most of Italy and Poland, Thursday 4 October 1582 was followed by Friday 15 October. France followed in December, the Catholic Low Countries a few weeks later.
Every year a country waited cost it more, because the Julian calendar kept leap days in 1700, 1800 and 1900 that the Gregorian dropped. Denmark and Norway and the Protestant German states switched on 1 March 1700, just after the first of those leap days, so they dropped eleven dates, the old calendar's 29 February among them. Britain and its colonies dropped eleven in 1752, and Sweden eleven in 1753. Only two of today's countries have a part that dropped twelve: Switzerland, whose last communes, Schiers and Grüsch, went from 25 December 1811 to 7 January 1812, and Uganda, which the list records switching under British rule on 13 January 1894. The Orthodox east and the Caucasus, switching in 1915 to 1923, dropped thirteen: in Russia, Wednesday 31 January 1918 was followed by Thursday 14 February, which is why the October Revolution is now remembered on 7 November.
How many dates each country dropped
Today's countries by the number of dates left out when the Julian calendar was replaced. A country appears in two rows when its regions switched in different centuries (13 do). The last row moved from other calendars, where no dates are dropped.
Sweden tried to be clever. From 1700 it planned to skip all eleven leap days over forty years and slide gently into step. It skipped 1700, forgot in 1704 and 1708, then gave up and went back to the Julian calendar by adding a day: 30 February 1712, the only one there has ever been. It finally jumped in 1753, Wednesday 17 February followed by Thursday 1 March. Sweden was not the only place to go back. The list records 8 returns to the Julian calendar: Groningen in 1594, Appenzell Ausserrhoden in 1597, Nova Scotia under British rule in 1710, Lorraine in 1735, Courland in 1796 and the Lithuanian lands under Russia in 1800, while Ulster's Gaelic lordships had a papal dispensation to go back by 1641. France abandoned the Gregorian calendar altogether for its Republican calendar from 1793 to the end of 1805.
Outside Europe the switch usually came from a different kind of calendar altogether. Japan went from the second day of the twelfth month of Meiji 5 straight to 1 January 1873; Korea switched in 1896, China in 1912, Vietnam in 1954. Saudi Arabia, which keeps the Islamic calendar, moved public sector pay to the Gregorian calendar only on 1 October 2016. Four countries, the article says, still have not adopted it as their civil calendar: Afghanistan, Ethiopia, Iran and Nepal.
Britain's switch came with the Calendar (New Style) Act 1750, which also moved New Year's Day from 25 March to 1 January (Scotland had done so in 1600) and applied to all the Crown's dominions "in Europe, Asia, Africa, and America", so the Thirteen Colonies changed with it: George Washington, born on 11 February 1731 in the old style, celebrated his birthday on 22 February. To stop anyone gaining or losing, rents and taxes fell due on their old natural days, which is why Lady Day on 25 March became 5 April. The famous slogan comes from a Hogarth painting satirising an election, and no riot appears in the official records.
The driving table records 62 of today's countries changing side at a known date. All but 3 moved from left to right. The busiest decade was the 1920s, with 16 switches, as the states carved out of Austria-Hungary, Italy, Spain, Portugal and its colonies all moved right; a second wave in the 1960s and 1970s took former British colonies into line with their neighbours: Gambia in 1965, Sierra Leone in 1971, Nigeria in 1972, Ghana in 1974, Sudan in 1973 and Myanmar in 1970.
Every dated change of side
Each dot is a country, at the year the table gives for its switch. Hollow dots: the table gives the date but neither it nor the article describes the change. Hover or tap a dot.
The most famous switch is Sweden's. A 1955 referendum voted 83% to keep driving on the left, but cars were multiplying, most were already left hand drive, and its neighbours drove on the right. So on Sunday 3 September 1967, Dagen H, all traffic stopped at 04:50, carefully changed sides, and set off again at 05:00. Accidents fell at first; by 1969 they were back to normal. Iceland followed in May 1968.
Only 3 of today's countries went the other way: Namibia in 1920, under South Africa; Timor-Leste in 1976, after switching right with Portugal in 1928 and back to the left under Indonesian occupation; and Samoa in 2009, to use cheaper right hand drive cars from Australia, New Zealand and Japan. Okinawa drove on the right under American rule from 1945 until 30 July 1978, and Uruguay drove left from 1918 to 1945. The United Kingdom is the best known holdout: in the late 1960s it looked at switching and decided it would be unsafe and too costly. Today 54 of today's countries drive on the left, among them Japan, India, Indonesia, Thailand and most of southern and eastern Africa, and in Europe only Cyprus, Ireland, Malta and the United Kingdom.
The metric system began in revolutionary France in 1795 and spread through conquest, unification and trade: Portugal in 1814, the Netherlands and Belgium in 1820, Spain and Latin America by the 1860s, the new German Empire in 1872. The table of when each country's official metrication process started runs from France to Samoa in 2015; the median country in it started in 1920.
When metrication started
The year the table gives for the start of each country's official metrication process. Ringed dots: countries where the table says imperial or customary units remain in official use alongside metric. Hover or tap a dot.
Starting is not finishing. The United States made metric units lawful in 1866 but never displaced its customary units, and according to the US National Institute of Standards and Technology it is one of three countries without mandatory metric laws, with Liberia and Myanmar. The United Kingdom began a ten year programme in 1965, gave up compulsion in 1979, and in 2023 confirmed it would keep pints of beer and miles on road signs. Canada halted in 1985. These are the countries the table lists as metric and something else: Canada, Liberia, Myanmar, the United Kingdom and the United States.
New Zealand was the first country where women could vote in national elections, in 1893. Then came Australia (1902, but not yet for Aboriginal women), Finland (1906) and Norway (1913), then a rush around the end of the First World War: by 1918 women could vote in 23 of today's countries. The largest wave came after the Second World War and with independence from empire: 81 countries first gave women the vote in the 1940s and 1950s.
The first vote, and votes on equal terms
The 18 countries where the table gives a first year for a restricted vote and a later year for full or equal terms. Most countries have a single year in the table.
Those two years can be far apart. In the United Kingdom women over 30 with property could vote from 1918, but only in 1928 on the same terms as men; in Portugal a restricted vote came in 1911, was taken away, returned in 1931 and lost its last restrictions only in 1976. In South Africa white women voted from 1930 and all women, with all men, only in 1994. The stragglers are a mix of small democracies and Gulf monarchies: Liechtenstein in 1984, Samoa in 1990, Qatar in 1997, Bahrain and Oman in 2002, Kuwait in 2005, the United Arab Emirates in 2006, and Saudi Arabia, where women first voted in municipal elections in December 2015 (it has no national elections). Switzerland gave women the federal vote only in 1971, and the canton of Appenzell Innerrhoden held out until 1990. Eritrea and Vatican City hold no votes for anyone.
Every switch has its stragglers, and some countries appear again and again. The United Kingdom switched calendars 170 years after Rome, still drives on the left, began metrication only in 1965 and stopped part way, and gave women the vote on equal terms in 1928, a decade after the first partial vote. The Gulf states were among the last for votes; the Orthodox east was last in Europe for the calendar.
The last ten to switch
The latest dated switches in each table. Click a name to see it on the map.
All 197 of today's countries. Click a column to sort, a row to see it on the map. Calendar years in brackets are part of the country first; "colony" marks a year I take from the colonial power; votes show the first year and, where the table gives one, the year of equal terms.
Sources. 19 English Wikipedia articles, saved with their revision numbers in 2026 (listed in the paper). For the calendar the primary source is the table in "List of adoption dates of the Gregorian calendar by country" (146 rows, each a historic area within one of 51 present countries, with the last day before and the first day after the change and the number of dates omitted). I checked it against the adoption tables in the "Gregorian calendar" and "Julian calendar" articles and the country by country prose of "Adoption of the Gregorian calendar"; the 19 places where they differ, mostly because the list has finer regional detail, are set out in the paper. For driving I used the country table in "Left- and right-hand traffic" (231 rows) and its prose; for metrication the status table in "Metrication" (77 rows); for votes the table in "Women's suffrage" (199 rows), with its notes. Every table was read cell by cell, with footnote markers removed, and is published as it was read.
Matching. Each row is matched by name to one of today's 197 countries (Natural Earth). Historical states are drawn with the modern country that covers most of them (Bohemia with Czechia, the Ottoman Empire with Turkey, Yugoslavia with its successors), and the popup says so. For the calendar, the table's 1582 row covers Spain, Portugal and France "and colonies thereof", and its 1752 row "the First British Empire"; I date 27 former colonies in the Americas and the Philippines by the power that ruled them then. That is my mapping, shown with a dashed outline. Where the tables disagree I keep the main table's year and give the other in the popup.
Reading the years. The calendar year is when the whole of today's country was first on the Gregorian calendar; earlier regional switches show as "part", and returns to the old calendar are kept. The effective year is that of the first new style day, so 21 December 1585 followed by 1 January 1586 counts as 1586. Days dropped are the list's "number of dates omitted"; every one matches the rule in the "Gregorian calendar" article (ten until February 1700, eleven to February 1800, twelve to February 1900, thirteen after), read at the first new style day, except Alaska, where the date line moved too. The driving year is the table's "date of switch"; where it gives none, today's side is assumed throughout, and where it gives a date with no description of the change the earlier years are flagged. The metric year is when the official process started, not when it finished. For votes, a single year in the table is used as it stands; where the table gives a restricted first year and a later full or equal year, both are kept.
What this is not. Wikipedia's tables are compiled by many hands and some cells are unsourced; I have not checked them against primary records. The gaps are real gaps in the sources, not countries that never switched: most of today's countries use the Gregorian calendar and the metric system without a date in these tables. Shares of population use today's populations.