\[ \boxed { x{\frac {\rm d}{{\rm d}x}}y \left ( x \right ) -\sin \left ( x-y \left ( x \right ) \right ) =0} \]
Mathematica: cpu = 3.054888 (sec), leaf count = 22 \[ \text {DSolve}\left [x y'(x)-\sin (x-y(x))=0,y(x),x\right ] \]
Maple: cpu = 0.982 (sec), leaf count = 0 \[ \text {could not solve} \]