Curious about the added lore to the TES storyline, I spent some time on UESP reading up on it. To my amazement however, there is no detail or mention of when the Dragon War occured.

http://www.uesp.net/wiki/Lore:Dragons

http://www.uesp.net/wiki/Lore:Wars#The_Dragon_War

Essentially, all of the lore and history of Man and Mer develops with the end of the Merthic Era and is detailed in various information by King Harald's bards and other sources. Prior to Skyrim, the "Dragon War" wasn't very well known, and it still isn't quite that. After playing through the storyline, it is still rather unclear as to when in history this war actually occured. It is eluded in the game that Dragons ruled over men and mer in the dawning era, but there is not mention of this in prior history. What is troubling me is that Bethesda's loremasters have not released any updated information or any novels in the game detailing the war, while the archaeic history of Ysgramor is detailed quite well, and that is supposedly supposed to occur before the end of the Dragon War atop the Throat of the World. It seems to me that the exact dates of the war and information of it is either unknown or Bethesda isn't telling us something. My question to anyone who may read this and respond is if you have anything to add, suggest, or clarify as to when this war may have occured and why it is not detailed as well as it should have been by Bethesda's loremasters.

Its a sort of oversight, if the link in my siggy is correct just over a year ago I said, if this Game had anything to do with Dragons, then it is something we've never heard about before, ever. and alot of things need arrangement like was the night of tears before? or after the War. what about the Dwemer why aren't there concrete interactions between them and the Nords during the relevent time frames?

for something as elaborate as Dragon priests ruling with an Iron fist after coming to Tamriel one may or may not be able to say that it was a structured burning of the histroy, what of Atmorans? where they ultimately ruled by Dragons? what are the relationships and why the inconsistencies? whats with the lack of info even though skyrim is BRIMMING with artifacts and history from those ages? and Olaf? or that Windhelm is an Ancient Nord built city but next to no information on its history?

alot needs sorting out.

It says it happened during the Merethic Era, so sometime before the First Era. Likely near the middle, as that is when the races start to develop more culture.