You need to identify at what time in history the source was created. Be as precise as possible. If you know the year, state that. If you do not know the exact
year, be as specific as you can based upon what you know about the source. For example: decade, century or historical era.
The Gallic Wars
was created by Julius Caesar himself during his campaigns in Gaul in the 50s BC.
This book survives from the time of the English Reformation.