Board Thread:Wiki-Related Discussion/@comment-4975807-20180520221943/@comment-6302057-20180521124017

All of the confusion starts in After Fourth Curse (A4C)...

With the current system, During Fifth Curse and After Fifth Curse occur within A4C. The Coven's curse forces everyone into the past.

In 7x22, Past Zelena and Past Charmings help the heroes, then return to SB, presumably with wiped memories to maintain the timeline (think Rumple 3x22). Once Regina casts her final curse, everyone from the future returns to the future and after that the realms are unified (in the future).

Here's a rough visual timeline I smashed out: https://postimg.cc/image/6sh4cv3nr/