It is actually and abbreviation of the phrase Day of Days, first used in World War I by the American Expeditionary Force in 1918, and this works with all languages that use this code, Jour J in French, E eguna in Basque, Ziua-Z in Romanian, and Dan D in Slovenian.
D-Day stands for DEBARKATION DAY...this is from a World War II veteran the letter D. D-Day was just a name given to the day on which a particular operation commences or is to commence. For an hour they would call it H-Hour, for a day D-Day. There is actually an entry in the military times with all of these classifications. C-day, M-day, F-hour, H-hour, all of these names are there. All just classifications for an unnamed day in which action was to take place.
Even better, important assaults are called D-Day because the D at the beginning means Day, so the word means Day-Day, or Day of Days and the same for H-Hour
Note: There are comments associated with this question. See the Discuss:What_does_the_D_in_D-Day_stand_forto add to the conversation.
dday means doomsday
Normandy
in Normandy, France
6 June 1944
For Skirmish Dday you have to call. I assume it is the same for Oklahoma and other big dday games also.
http://www.britannica.com/dday
Dday
jaankaree, aank-dday
dday what a final attack of the axis powers on the allies no mate... dday was he day that the retard from America predicted the end of the world on 21st may 2011.. and failed. haha to all the believers.. if it was me saying we were gona die tomorrow.. you wouldn't believe me would you. but yeah dday is now 21st october 2011... which ain't gona happen either. so yeahh that's all there is. hope this helps :)
In Normandy, France. All over the beaches
Was d-day a success? Yes. DDay is this
how many tanks were there durind dday