Suppose body A, at rest in its reference frame, is passed by body B which is travelling at a constant 0.6 c, heading toward Z, a point 6 light years away by A's reckoning, and as bodies will, they synchronise their watches.
A decade later by A's watch (and 8 years later by B's), body B arrives at Z. This will not be observable from A for another 6 years.
Body C, also travelling at 0.6 c, immediately then passes body A, synchronising watches in accordance with ancient spacefaring custom. Body D, making the same speed, passes body B and observes the same politeness. Bodies C and D both head for a point equidistant between bodies A and B to enjoy a good gossip and to compare watches.
Do the watches of C and D show a two year offset? Or are they identical?
If they are offset, how does this square with body B's perspective in which it is body A's watch which is running slow? If they are identical, how is this achieved?
With special relativity based discussions of the twin paradox, the change in reference frames affecting one twin and not the other seems to often be invoked to explain the discrepancy in aging. I would therefore be curious to hear an examination in which both twins changed reference frames at the turnaround point and headed to a simultaneous meeting.