I need help with this question. I do not know how to start. Please explaining the problem for me.

Consider the differential equation y 0 = f(t, y) and suppose that for all t and y we have that f(t, y) = f(t + 2, y). Show that if y1(t) is a solution to the above equation, then y2(t) = y1(t + 2) is also a solution.