Not really. As Chief Justice Chase said in his decision, "Acts of hostility by the insurgents occurred at periods so various, and of such different degrees of importance, and in parts of the country so remote from each other, both at the commencement and the close of the late civil war, that it would be difficult, if not impossible, to say on what precise day it began or terminated. It is necessary, therefore, to refer to some public act of the political departments of the government to fix the dates, and, for obvious reasons, those of the executive department which may be and in fact was, at the commencement of hostilities, obliged to act during the recess of Congress, must be taken...The proclamation of intended blockade by the President may therefore be assumed as marking the first of these dates, and the proclamation that the war had closed as marking the second."
April 19th was arrived at for legal reasons, and not because that marks the first act of the war. Your argument makes as much sense as saying that for the U.S. the Second World War began on December 8th since that was the day of the formal declaration rather than on December 7th, the day of the Japanese attack.
As President Roosevelt said at the time:
That's the same use of language as the Confederate Declaration of War against the United States, May 6, 1861.
But our FRiend, DiogenesLamp, has adopted the insane position that any comparison of Fort Sumter with Pearl Harbor "ist verboten", and therefore excluded from his own analyses.
But in fact that comparison is rather good, in several respects.