Question

A major event in the French Revolution happened on July 14 1789 when a mob stormed the Bastille a notorious prison in Paris how can historians today use primary sources to determine that this date is accurate

Answer 1

Sources such as diaries though not very reliable can be used if there are a large amount of them showing the same date and event. Historical books written about the event especially those closer to the time would be able to help determine that the date is accurate as well.