Suppose, a long object is at rest in S frame. There is A (On the long object) and B (Near the long object, on the ground) observer in the middle of the long object. There are two clocks located on both end of long object. We suppose, both A and B is at origin of S frame and clocks at some -x and +x location. The clocks is synchronized for both observer. Now, at t=0 the object starts moving to right with respect to B observer. Now the long object is at rest in S' frame and moving relative to S frame. We can see from the diagram that clocks is still synchronized for A observer, but no longer synchronized for B observer. The time reading changed instantly for B. Time decrease in left clock and increase in right clock for B. After the frame change, the difference between the time readings of clocks remains constant for B. We can see that both clocks is far from B in this case. Now, suppose a situation where observer A, B and left clock are on origin of S. Now A and B is at left end of long object. We can see that left clock reading is not changed instantly for B on frame change, but right clock's reading increases for B. We can see that left clock is near to B in this case. Now, suppose a situation where observer A, B and right clock are on origin of S. Now A and B is at right end of long object. We can see that right clock reading is not changed instantly for B on frame change, but left clock's reading decreases for B. We can see that right clock is near to B in this case. In all the case clock reading changed instantly when the clock is not near to the B observer. I think the distance of observer from clocks is the cause of instant change in readings, and direction of motion of clocks is the cause of in which way the clocks desyncs, up or down. I would like to read your thoughts. Please, feel free to point out any error if have made here.