Wikipedia:Reference desk/Archives/Mathematics/2015 June 20

= June 20 =

Date/Month/Year count
Guys I don’t understand the following i.e. Democritus was born c. 460 BC and died c. 370 BC. I have a feeling that I don’t possess the knowledge of how the ancient date/month/year countings. I understand that ‘c.’ stands for ‘circa’, can someone explain this to me please, in a simple term? Also ‘who comes first, second and third out of Plato, Democritus, Empedocles?. Important: Please give me an article to learn the ‘date/month/year count’.

Regards.

Space Ghost (talk) 19:22, 20 June 2015 (UTC)
 * Imo not really a math question but here goes. First of all, BC isn't an ancient system but roughly equivalent of negative years in the current system. Not quite the same though since there is no year 0, so the year before year 1 is year 1 BC. (Usually the more politically correct BCE is used for BC nowadays.) So Plato (born c. 425 BC) was born about 35 years after Democritus (born c. 460 BC) who was born about 30 years after Empedocles (born c. 490 BC). My understanding is that calendars as we know them weren't used at that time and it took a lot of scholarly detective work to translate the scant clues given in ancient texts to numerical years that moderns can make sense of. But that's why you see all those c.'s running around, it does mean 'circa' and indicates it's an approximation; sometimes there just aren't enough clues for the detectives to produce an exact number. See Anno Domini, Common Era and 0 (year) for more info. (Why isn't this covered in a single article?) --RDBury (talk) 20:34, 20 June 2015 (UTC)
 * Here, BC means "Before Christ", so Democritus was born about 460 years before Jesus Christ was born, and died about 370 years before he was born. That is why it looks like he died before he was born: you are counting backwards to the birth of Christ. After Christ was born, years are counted in the regular way, and you might see the suffix "AD". You won't see this if it is obvious from the context (i.e. if someone is born in 2015, you wouldn't see their birth date listed as "2015 AD"), but you will see if it someone was born before Christ and died after Christ was born (e.g. someone who lived from 30 BC to 10 AD). Hope this helps. OldTimeNESter (talk) 15:22, 21 June 2015 (UTC)
 * Since "BC" means "Before Christ" it follows the year - seventeen Before Christ = 17 BC.  "AD" is a contraction of "Anno Domini" (in the year of Our Lord) and precedes the year - in the year of Our Lord One Thousand Nine Hundred and Sixty = AD 1960.   Calendars as we know them have been used since the dawn of civilisation.   The idea of counting from a fixed point (the "era" reckoned from an "epoch") came along later.   From memory, one such, the Era of Nabonassar, runs from 27 February 747 BC. 87.81.147.76 (talk) 17:46, 21 June 2015 (UTC)
 * Two notes. First, "Anno Domini" means "in the year of the lord", not our lord; you don't have to be a Christian to use it. Second, BC and AD year numbering is based on the year when Christ was thought to have been born, but that calculation was wrong. Blame Dionysus Exiguus. --70.49.171.136 (talk) 14:35, 23 June 2015 (UTC)
 * Yes yes yes, thank you friends, acknowledged... I'm also gonna read/learn the articles, as soon as I become free... Thank you all. -- Space Ghost (talk) 21:38, 21 June 2015 (UTC)


 * I've given up trying to get the world to put AD before the number. —Tamfang (talk) 22:27, 21 June 2015 (UTC)
 * Are you happy with CE after the number? -- ToE 23:20, 21 June 2015 (UTC)
 * Lol. -- Space Ghost (talk) 18:10, 22 June 2015 (UTC)
 * Until recently, the following information appeared in Common Era:

A complete Easter cycle consists of 532 years and begins in a leap year. Dionysius was unaware of the 532 - year repeating period, but he was aware of the cycle of 95 years over which the date of Easter will usually repeat, and he understands that it is the clash with the four - year leap year cycle which invalidates it after a long period. He listed Easter dates for the remaining seven years of the current 95 - year cycle and then named the first year of the new cycle as AD 532 instead of 248 of Diocletian and the Martyrs because he wanted to count from the Incarnation. However, he did not know exactly when the Incarnation was (nobody knows). This is evident from the comments in Argumentum XV of his Liber de paschate sive cyclus paschalis, penned by a later commentator. The date of the Annunciation is given as Sunday, 25 March and the interval to birth as 271 days. The birthdate is given as 25 December, but 271 days from 25 March is 20 December. The writer then says Christ was born on Tuesday, 20 December. The date of Sunday, 25 March implies he considered Christ to have been born in 4 BC, which is the date accepted by the majority of scholars. Dionysius labeled the column of the Easter table in which he introduced the new era "Anni Domini Nostri Jesu Christi".

I think this could profitably be added to Dionysius Exiguus, but in view of 70.49.171.136’s comment I thought I should run it past you first. 87.81.147.76 (talk) 09:32, 25 June 2015 (UTC)