--- title: How our calendar was made: Romans, Julius Caesar and Pope Gregory — a lesson of Mova's school · trees and pragmatics description: «How our calendar was made: Romans, Julius Caesar and Pope Gregory», a lesson of the world course of Mova's primary school, sentence by sentence with dependency trees and pragmatics. It begins: A calendar is a set of rules for counting days into months and years so that the dates stay in step with t --- [Mova](https://md.mova.elamur.ai/free/en/) · [this page in HTML](https://mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/) [home](https://md.mova.elamur.ai/free/en/) / [corpora](https://md.mova.elamur.ai/free/en/corpora/) / [school](https://md.mova.elamur.ai/free/en/corpora/school/) / [World](https://md.mova.elamur.ai/free/en/corpora/school/world/) / How our calendar was made: Romans, Jul… # How our calendar was made: Romans, Julius Caesar and Pope Gregory Lesson 116 of the world course of Mova's primary school: 22 sentences, each with its syntax tree and pragmatics. The lessons are written for Mova, and their agreed trees are part of Mova corpus 0.4 (CC BY-SA 4.0). How Mova does on its tests: [the lesson at school](https://md.mova.elamur.ai/free/en/school-run/world/116-how-our-calendar-was-made/). - [0](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/0/) — A calendar is a set of rules for counting days into months and years so that the dates stay in step with the seasons. - [2](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/2/) — The oldest Roman calendar started the year in March, so September ("septem" is 7 in Latin) really was the 7th month. - [3](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/3/) — When January and February were moved to the front, the old names stayed behind, like a kid who keeps the nickname "Shorty" after growing tall. - [5](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/5/) — In 46 BC Caesar made one year 445 days long to catch up, and from 45 BC his Julian calendar had 365 days with a leap day every 4 years. - [6](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/6/) — Caesar's year was about 11 minutes too long. - [7](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/7/) — Tiny, but after about 1,600 years the calendar had slipped 10 days, so in 1582 Pope Gregory XIII cut 10 dates out once and changed the rule: a century year is a leap year only if it divides by 400. - [8](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/8/) — This Gregorian calendar is the one most of the world uses today. - [9](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/9/) — Countries switched at different times: Britain in 1752, Russia and Ukraine in 1918. - [10](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/10/) — So old dates can come in two versions, "old style" and "new style", and a historian must always say which calendar a date is in. - [11](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/11/) — The oldest Roman calendar began the year in March, so September, October, November and December were months 7, 8, 9 and 10. - [12](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/12/) — In Latin, septem means 7, octo means 8, novem means 9 and decem means 10. - [13](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/13/) — July is named after Julius Caesar, and August after Augustus, the first Roman emperor. - [14](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/14/) — In 46 BC Julius Caesar made one year 445 days long, 80 days more than 365, to put the calendar back in step with the seasons; it was called the year of confusion. - [15](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/15/) — Caesar's Julian calendar, from 45 BC, had 365 days and a leap day every 4 years, so its average year was 365 days and 6 hours. - [16](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/16/) — The Julian year was about 11 minutes too long, which adds up to about one whole day every 130 years (11 × 130 = 1,430 minutes, close to the 1,440 minutes in a day). - [17](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/17/) — In 1582 Pope Gregory XIII brought in the Gregorian calendar: Thursday 4 October was followed by Friday 15 October, skipping 10 dates. - [18](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/18/) — In the Gregorian calendar a century year is a leap year only if it divides exactly by 400, so 2000 was a leap year but 1900 was not. - [19](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/19/) — Britain switched in 1752, when 2 September was followed by 14 September, skipping 11 dates. - [20](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/20/) — Historians think the famous riots of people shouting "give us our eleven days" probably never happened. - [21](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/21/) — Russia and Ukraine switched in 1918, when the gap had grown to 13 days (it had been 13 days since 1900), so old papers may show dates as "O.S." (old style, Julian) and "N.S." (new style, Gregorian). - [22](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/22/) — The Ethiopian calendar has 12 months of 30 days and a short 13th month of 5 or 6 days; its year number is about 7 or 8 behind ours and its New Year is in September. - [23](https://md.mova.elamur.ai/free/en/corpora/school/world/116-how-our-calendar-was-made/23/) — Shakespeare and Cervantes both died on "23 April 1616", but England used the Julian calendar and Spain the Gregorian, so they died about 10 days apart. - ← previous: [What day of the week will it be?](https://md.mova.elamur.ai/free/en/corpora/school/world/115-what-day-of-the-week-will-it-be/) - next →: [Other calendars: Chinese New Year, Islamic and Jewish calendars, and Christmas in Ukraine](https://md.mova.elamur.ai/free/en/corpora/school/world/117-other-calendars/) - ↑ back to [World](https://md.mova.elamur.ai/free/en/corpora/school/world/)