Board Thread:The Reference Desk/@comment-82.20.113.152-20130213135009/@comment-82.20.113.152-20130213193242

Well, the history of the universe in Series 5 clearly has differences from that of the universe of subsequent series (e.g. Amy has parents in one, and in the other she never has), so therefore it has to be a parallel/alternate reality. The incident with the Byzantium took place in the earlier reality, so River must have hopped from that to the post-Pandorica version. They're both distinct timelines.