How to use SDL2's timer functions to increase a variable by 1 every xxx ms

Using SDL2's time functions, this is what I want to happen inside my main loop:

if (angle < 360)
{
    ...every 300ms angle++ <-----how to use SDL's time functions to do this ?
}
else
{
    angle == 0;
}

I'll be using this angle variable as an arguement for SDL_RenderCopyEx to render a rotating texture...