My knowledge toward physics stay on high school level, and all i know about relativity are from wiki, so please make the explanation simple~ In wiki, it said it is possible and logical that B's time runs slower relative to A while A's time runs slower to B. But i still can't understand how this is possible without causing contradiction. Let's say A and B are relatively stationary and separated apart by distance d, this makes their clocks run at the same rate and display the same time. Then they start traveling toward each other at the same high speed when both clocks show 3 p.m. They will stop and meet each other at the mid-point between them since both speed are the same. Since B's time runs slower relative to A while A's time runs slower to B, if A's clock turns 4 p.m. when they meet, what time will B's clock show? after or before 4 p.m.?