Time-accuracy in keeping History

Aug 2017
From what time-period did the (mostly) accurate keeping of dates begin?
So from what time can we be sure that if a certain date is given, that it wasn’t extrapolated after the event?
For example: if a battle was fought on August 6th . From what time-period would there have been August 6th in the accounts for that battle written in the same period (instead of “in the summer” or “beginning of August”)?
In short: If you see a certain date in a history book, from when time period can you be certain that the event occurred on that date and not somewhere around that date?


Forum Staff
Aug 2016
The Julian Calendar was given to the Romans by Julius Caesar. That calendar is almost identical to the Gregorian Calendar that we use. The Julian and Gregorian Calendars are eleven days apart so it's easy for a writer to translate from one to the other (not that writers always do). Some dates are in the old Julian calendar because the writer didn't think the difference was important. Julian dates are identified as such by the initials (OS) meaning 'old style' - August 6 (OS).

Years can be problematic because the Romans did not always start their years on Jan 1. March 21 was a common date for the new year. They also used regnal years - 'in the sixth year of the Emperor Tiberius.' The first year of Tiberius began on the day he assumed the throne and ended on the first anniversary of that date. So each ruler had a different New Year's Day.

The Romans did not always number their days of the month. Instead there were certain landmarks in each month such as the Ides of March or the Kalends of October. Specific days were identified as 'three days before the Ides of April,' or 'six days before the Kalends of May.' But still, it's easy for a writer to translate these dates into a modern format.

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Forum Staff
Aug 2016
There's another issue. Medieval chroniclers (let alone ancient) might give different years for an event. Somebody got it right, somebody got it wrong. EG Siege of Graus 1064 - or 1065!
Yes, that's the issue with different days for the New Year. If the chroniclers were beginning their years on March 21, and the siege was in February of 1065 by our calendar, then it might be recorded as Feb 1064 because the ancient New Year hadn't happened yet.
Apr 2014
Liverpool, England
I cannot check my sources just now, but I believe King John of England came to the throne on Ascension Day - it followed that his regnal years were counted from Ascension Day in each year, and that being a moveable feast the years were all of different length.

But all this is missing the original point of when people started recording accurate dates of events such as battles. I think the answer is that for a long time this was very patchy. Tacitus's account of the year 69 AD is very detailed and often recounts events from day to day, and even hour to hour - and it is likely that his sources were well-informed on such matters. On the other hand, even in recent years it can often be quite difficult to pin down the exact dates of events. A startling example is the date of Hitler's visit to Paris in 1940, which people are still disagreeing about.

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