When did the 2 political parties swap ideals?

There have been multiple half swaps over some time. An example of this is that the Republicans and Democrats have switched many times just over the issue of war. In the late 1880's the Reps were basically imperialist and the Dems were very anti war. After Wilson, they basically switched and the Dems were more pro-war and the Reps anti. Though now both parties are pretty much pro-war unless it will benefit them to be anti-war.