dt = 1e-2;
t = 0:dt:20;
y1 = sin(t); h1 = hilbert(y1);
y2 = sin(t+1); h2 = hilbert(y2);
p1 = angle(h1); p2 = angle(h2); % Instantaneous phase (wrapped)
p = unwrap(p2)-unwrap(p1);      % Instantaneous phase difference

figure;
subplot(211);
plot(t,p1,'r',t,p2,'b');
subplot(212);
plot(t,p,'k');