From case study of carefully selected planar discontinuities we got clear evidence that orientation of the Solar Wind Discontinuity seriously affects timing of compressions/rarefactions propagating in the magnetotail. In agreement with a simple kinematic scheme we confirm that for slanted discontinuity time differences up to several minutes may arise depending on Y,Z coordinates of the spacecraft at the same X position. These effects are important when studying the tail dynamics and substorm triggering problem.