When did the civil start?

Answer 1

It never started, and never ended.

When the South fired on the US Army garrison at Fort Sumter, it could claim that it was only defending its own declared territory, and was not wanting a war. Any war would have to be declared by Lincoln of behalf of the Union.

Lincoln could not declare war without appearing to grant recognition to the Confederacy as a sovereign nation. (He was in bad enough trouble by declaring a 'blockade' of his own ports.)

So he simply appealed for volunteer-troops - and no-one was in any doubt about the proposed function of these troops.

At the end, there was the surrender of Lee to Grant at Appomattox, and it is slightly unclear why one General-in-Chief, surrendering to another, could not simply order his troops to lay down their arms. If Lee was only wanting to surrender his own Army of Northern Virginia, he should have surrendered it to the army that defeated it, that is, George Meade.

So other, smaller operations continued for a while, and the Confederate cabinet held its last meeting in a small town in Virginia in May. That might be described as the end of the Confederacy, and therefore the war.

But even then, there were more small operations in Texas, and also many Confederate officers escaped into Mexico and refused to surrender.

As there was never a peace-treaty (because Congress did not acknowledge that it had been fighting a foreign enemy), there are Southerners to this day who declare that the war never ended.