Bloodiest day in world history

I would guess that the bloodiest wartime day in world history would be probably the day we bombed Hiroshima, but I do not know that anybody has ever tallied it up completely.  The bloodiest peacetime day would probably be the day the earthquake struck in January or maybe the day of the Thera explosion in antiquity.  Again, I am not aware of anybody ever making the calculations.

 The bloodiest peacetime day would probably be the day the earthquake struck in January or maybe the day of the There explosion in antiquity.  Again, I am not aware of anybody ever making the calculations.

What is this exactly?

The Earthquake in Haiti, killed something like 250-300,000, which is more than the Tsunami of 2004 killed.I bring up Thera because there is speculation that Thera's explosion and resulting destruction is the source of the Antlantis myths.

Jan. 23, 1556, Shaanxi (Shensi) province China; earthquake 830K killed.Hiroshima ([within]in 2-4 months of bombing) 90-166K killed, est 75K immediate; Nagasaki (same time frame) 60-80K, est 40K immediate.Tokyo firebombings: 100K plus.Dresden, est at the time... 150K-250K deaths. 2010 report "up to 25,000 civilian casulties". Other ests vary... 24-40K. (killed)Somme: Almost 60K British casualties the first day (19,240 killed).Antietam / Sharpsburg... Union: 2,108 killed, 9540 wounded, 753 caputed /  missing (of 75,500)                                  CSA:  1,546 killed, 7,752 wounded, 1,018 captured / missing (of 38,000)Just some numbers I found....

You could probably pick just about any titanic battle from the French Revolutionary wars and make the argument.  There were something like 40,000 deaths at Koniggratz on 3 July 1866 during the Austro-Prussian War and almost 25,000 at Waterloo, you could also look at some of the opening days of Barbarossa in 1941 or WWI. The French suffered almost 1 million casualties in August of 1914 alone even guessing 20% deaths that is still 200,000 dead in one month.  Picking a bloodiest day is pretty difficult because if you are talking about the world, especially the World Wars do you figure just a battle or the totality of war dead on one specific day?  Peacetime days are just as difficult.  How many people just plain old die every day in the world?  I would guess that number alone is in the millions.

I read somewhere that Cain was the greatest mass murderer in history, as he slew fully one quarter of the earth's population