75

In the particular case of Eratosthenes measuring the radius of the earth, it was done by observing the length of shadows at midday on the summer solstice, in cities that were north-south aligned (to within a few degrees). It was known that the sun was directly overhead on the solstice in the city of Syene in Egypt. But further north in Alexandria on the ...


50

Edinburgh Castle's tourist attraction, the One O'Clock Gun, originated as an audible version of the Nelson Monument time ball. The Nelson time ball has dropped at 1:00 pm ever since it was installed in 1853. Accordingly, the One O'Clock Gun also fired at 1:00 pm. Anything else would have been potentially confusing. Time balls were important for maritime ...


42

Most likely because it wasn't until the modern era that anyone really needed, or could achieve, much precision with time measurements. Prior to modern timekeeping, people pretty much lived on daily and seasonal schedule. The main thing you'd need to know was how close between sunup and sundown you were (and which side, but that's typically obvious by ...


21

In general, dating was complicated, and different conventions existed simultaneously in England at that time. For the specific example of William the Conqueror's coronation, we have different sources within the following decades implying that it was in 1066 or 1067, anno Domini. The precision sought in the question did not exist, at least in the same form ...


20

From Scientific American: Hipparchus, whose work primarily took place between 147 and 127 B.C., proposed dividing the day into 24 equinoctial hours, based on the 12 hours of daylight and 12 hours of darkness observed on equinox days. Despite this suggestion, laypeople continued to use seasonally varying hours for many centuries. In terms of when ...


18

Essentially the extra quarter of a day that the Julian leap year added was slightly longer than the 0.242 of a day left over in the actual solar year. It affected Pope Gregory XIII because the Christian holidays were being celebrated on the wrong days. This was noticed by the Pope's astronomers and prompted the need for change. What's the science behind ...


17

One example would be the Amondawa who are a group of indigenous peoples of Brazil. The Amondawa are a sedentary group that utilize various forms of hunting fishing and agriculture to provide for their community, yet according to researchers the Amondawa lack an "abstract concept of time." The University of Portsmouth and the Federal University of Rondonia ...


16

For the most part, church and celestial events. In particular, midsummer and midwinter and the equinoxes were both easy to detect and were important events, at least in the colder climates of Europe. One problem with this approach was that the Julian calendar, which was used pretty much everywhere during the middle ages, by the 1500s had gotten seriously ...


16

All through history, people needed fair, repeatable measurement of physical quantities. How much grain am I buying? How much land do you have (so it can be taxed)? How much flour and water do I use for my bread? Since most trade was local, they used whatever system they came up with. So long as the people nearby understood it, and it was based on some ...


15

there are 3 years, not two, that have to be coordinated. Stellar, Solar and Lunar. The duration of none of these three can be expressed in whole days. (we have leap years because of this). Every old calendar, including that of Mayans, Egyptians and Sumerians, worked. The only difference is how did they corrected for the difference of the solar, the lunar and ...


15

In 1940, Spain changed its time zone from GMT to GMT+1, as Franco thought that it would be a good idea to have the same time as Nazi Germany and Fascist Italy (his political allies) after Germany occupied France. The United Kingdom modified its time zone too, but reverted its decision in 1945. In the 80s, the PSOE (political party at government) ...


15

Most people just rose at dawn, or when the birds started their noise, like a rooster. Those few who really had to wake up earlier were usually woken up by 'specialists', like the Knocker up Letting someone else wake you is just shifting the problem. How would those people wake up? As long as a human keeps a fairly regular circadian rhythm with sleeping at ...


15

To add to the answer of PhillS: there was essentially no method of exact time synchronization in two remote places before 17th century. The method of observation at noon at two places only works UNDER THE ASSUMPTION that the places are on the same longitude. The longitudes of Syene and Alexandria are approximately equal, which Eratosthenes knew (when ...


14

Some astronomical events, viz. eclipses, can be reliably predicted to the day. I think they are the best method to identify a date exactly. This webpage provides some insight on the topic. It is basically a list of recorded solar eclipses, where the first one would be on 22 March 2134 BCE. There is however some uncertainty about whether or not the event ...


12

After some reading about the early Roman Calendar, it is relevant to note that originally the calendar had only ten months and began on March, with an uncounted “winter” period after December. The number of days on each month were more or less flexible, and they usually tried to align the 15th of March, the mid of the month, with Ides, a full moon. At the ...


12

Why does everyone use seconds/minutes/hours today? These units were adopted in the west in ancient times, by the Greeks, who borrowed it from their middle eastern neighbors, the Babylonians, who had used it before them. It's all because time-keeping, with seconds, minutes, and hours, originates with astronomical observation, and the art and science are ...


12

Sir Sandford Fleming invented Worldwide Standard Time between 1876 and 1879: After missing a train in 1876 in Ireland because its printed schedule listed p.m. instead of a.m., he proposed a single 24-hour clock for the entire world, located at the centre of the Earth, not linked to any surface meridian. At a meeting of the Royal Canadian Institute, on ...


11

What time was it in Dawson Creek, BC at 1900-01-01 00:00:00 +0000? The pedantically correct answer, based on the IANA Timezone Database, is that it was 1899-12-31 16:00:00 (-0800) at 1900-01-01 00:00:00 +0000. The IANA time zone entry for America/Dawson_Creek is shown below. # Zone NAME GMTOFF RULES FORMAT UNTIL Zone America/...


11

"BPE" stands for "Before Present Era", and is equivalent to the more familiar BP (Before Present = 1950). It is a new "standard" abbreviation that I have seen appearing over the last decade or so (more commonly in publications from the USA). It is worth noting that the original BP standard was established solely for the reporting of radiocarbon dates. ...


9

1927 saw Shanghai change control from local warlords to the Kuomintang Nationalist Government, who then purged the Chinese Communist Party on April 12 and then declared Shanghai to be a municipality in the Republic of China. Presumably the time change to GMT+8 from a more local mean time was a combination of desire for modernity and to show that Shanghai ...


9

None of the Hindu mythological books or puranas mention the names of the week , today what we use as VAAR ( Ravi , Som , Mangal, Budh . Brihaspati, Shukra, and Shani ) are the translated version of the western system , it was only the THITHI as per the Lunar calendar followed all over. the names of the week is recent and has no origin in Indian Mythology ( ...


9

The general concept of a date line preexists Caroll. By the 17th century possible locations for the line had been proposed See Here. People living at the same general time also recognized the notion of a date line. In 1872, Jules Verne wrote Around The World In Eighty Days in which crossing the date line is a plot point. In 1888, this map was produced ...


8

The ancient Hindus did not regularly use "days of the week" (although they are attested). The reason for this was that the Hindu calendar before 1100 AD used mean times (called madhyama) and this can shift days from one month to another. They did have a division into days assigned as one day to each planet as follows: Ravivara Somavara Mangalavara Budhavara ...


8

I'm actually deeply suspicious about the data used used on TimeAndDate for historical times, and I suspect things were a lot more messy on the ground in China in late 19th to mid-20th century, even with growth of telegraph etc. I did, however, poke around some postings in Chinese about Jon Skeet's Stack Overflow posting. One of the commenters here, wubotao, ...


8

BPE means Before Present Era. Now we know the words behind the acronym, we still don't know the meaning of those words. 21.12 dates Note: non-religious alternatives to BC (before Christ) and AD (anno domini – year of our Lord) are BCE (before common era) and CE (common era), and also BPE (before present era) and PE (present era). ...


7

Interestingly, when the time zones were established at the International Meridian Conference in 1884, the original idea was to have a single coordinated solar day. This meant that eventually, the hope was to have a single coordinated time throughout the world. The idea of dividing the world into time zones was merely supposed to be a step to getting to ...


7

Primarily for convenience of trade and communications across national borders. As the countries of Western Europe have become ever more closely linked, it makes life easier if people can agree on what time it is. The initial standardisation of times, in Great Britain at least, came with the railway - Bristol time was 11 minutes different to London, based on ...


7

Some societies use sunset as the end of one day, and the start of the next: this is recorded in Genesis, chapter 1; for example, the Athenians, or see the Jewish civil day Some traditional agricultural societies start the day with dawn, but Roman civil society defined the day as beginning at midnight. The day was divided into ante meridiem (am) and post ...


7

An important point which no one has mentioned - for most people, the need to wake up 'on time' is a product of the industrial revolution so before that there was no need for alarm clocks. Waking up at an approximate time was good enough. These days our lives are dominated by schedules and timetables - this is most obvious with transport, something which ...


6

The epoch of the Julian calendar (i.e., January 1st, 45 BC) was indeed synchronized with the first new moon following the previous year's winter solstice : It was probably the original intention of Caesar to commence the year with the shortest day. The winter solstice at Rome, in the year 46 B.C., occurred on the 24th of December of the Julian calendar. ...


Only top voted, non community-wiki answers of a minimum length are eligible