My basic time-line reference book is Fredriksen's Civil War Almanac (c2008), which is not 100% infallible, but I'm sure generally correct.
It says the Confederacy declared war on May 6, 1861 and Virginia ratified secession on May 23.
FYI, here is a link to a large selection of Confederate documents, including the Declaration of War.
I note the Declaration of War states:
"and whereas, the State of Virginia has seceded from the Federal Union and entered into a convention of alliance offensive and defensive with the Confederate States, and has adopted the Provisional Constitution of the said States;"
Virginia seceded in stages.
Virginia's state convention first reversed itself and voted for secession on April 17.
The final ratification came from Virginia's voters on May 23.
The vote was 97,750 in favor of secession, 32,134 against.
Western Virginia first declared its independence from Virginia on June 17.
The first Union forces crossed into Western Virginia around July 7.
The first major battle -- 1st Manassas / Bull Run -- began in mid-July.
Link is busted.
The South never declared War as far as I can tell. There are no documents.